few warnings during a build

[eirnym]

Describe the bug
Building on macOS using clang as a compiler. Few warnings catch my eye:

• logical-op-parentheses

	clang++ -DHAVE_CONFIG_H -I. -I../..  -I../../include -Wno-int-to-void-pointer-cast   -Wno-address-of-packed-member   -Wno-format-zero-length   -Wno-missing-field-initializers   -Wno-strict-aliasing   -Wno-implicit-fallthrough   -Wno-deprecated-declarations   -Wconversion-null   -Wsign-promo   -pedantic   -Wunused   -Wextra   -Wall   -I/opt/local/include -I/opt/local/include/SDL2 -D_THREAD_SAFE -I/opt/local/include/freetype2 -I/opt/local/include/libpng16 -I/opt/local/include -I/opt/local/include  -g -std=c++11  -O2 -msse  -Wall   -Wextra   -Wunused   -pedantic   -Wsign-promo   -Wconversion-null   -Wno-deprecated-declarations   -Wno-implicit-fallthrough   -Wno-strict-aliasing   -Wno-missing-field-initializers   -Wno-format-zero-length   -Wno-address-of-packed-member   -Wno-int-to-void-pointer-cast   -MT dos_misc.o -MD -MP -MF $depbase.Tpo -c -o dos_misc.o dos_misc.cpp &&\
	mv -f $depbase.Tpo $depbase.Po
dos_misc.cpp:366:68: warning: '&&' within '||' [-Wlogical-op-parentheses]
                if (uselfn && (!strcmp(psp_name, "NESTICLE") || reg_sp == 0x220A && mem_readw(SegPhys(ss)+reg_sp)/0x100 == 0x1F)) {
                                                             ~~ ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
dos_misc.cpp:366:68: note: place parentheses around the '&&' expression to silence this warning
                if (uselfn && (!strcmp(psp_name, "NESTICLE") || reg_sp == 0x220A && mem_readw(SegPhys(ss)+reg_sp)/0x100 == 0x1F)) {
                                                                ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 warning generated.

• format-security

	clang++ -DHAVE_CONFIG_H -I. -I../..  -I../../include -I../../src/aviwriter "-DRESDIR=\"\"" -I../../src -I../../src/mt32 -Wno-int-to-void-pointer-cast   -Wno-address-of-packed-member   -Wno-format-zero-length   -Wno-missing-field-initializers   -Wno-strict-aliasing   -Wno-implicit-fallthrough   -Wno-deprecated-declarations   -Wconversion-null   -Wsign-promo   -pedantic   -Wunused   -Wextra   -Wall   -I/opt/local/include -I/opt/local/include/SDL2 -D_THREAD_SAFE -I/opt/local/include/freetype2 -I/opt/local/include/libpng16 -I/opt/local/include -I/opt/local/include  -g -std=c++11  -O2 -msse  -Wall   -Wextra   -Wunused   -pedantic   -Wsign-promo   -Wconversion-null   -Wno-deprecated-declarations   -Wno-implicit-fallthrough   -Wno-strict-aliasing   -Wno-missing-field-initializers   -Wno-format-zero-length   -Wno-address-of-packed-member   -Wno-int-to-void-pointer-cast   -MT midi.o -MD -MP -MF $depbase.Tpo -c -o midi.o midi.cpp &&\
	mv -f $depbase.Tpo $depbase.Po
In file included from midi.cpp:100:
./midi_synth.h:44:26: warning: format string is not a string literal (potentially insecure) [-Wformat-security]
                LOG(LOG_ALL,LOG_ERROR)(message);
                                       ^~~~~~~
./midi_synth.h:44:26: note: treat the string as an argument to avoid this
                LOG(LOG_ALL,LOG_ERROR)(message);
                                       ^
                                       "%s", 
./midi_synth.h:48:25: warning: format string is not a string literal (potentially insecure) [-Wformat-security]
                LOG(LOG_ALL,LOG_WARN)(message);
                                      ^~~~~~~
./midi_synth.h:48:25: note: treat the string as an argument to avoid this
                LOG(LOG_ALL,LOG_WARN)(message);
                                      ^
                                      "%s", 
./midi_synth.h:52:27: warning: format string is not a string literal (potentially insecure) [-Wformat-security]
                LOG(LOG_ALL,LOG_NORMAL)(message);
                                        ^~~~~~~
./midi_synth.h:52:27: note: treat the string as an argument to avoid this
                LOG(LOG_ALL,LOG_NORMAL)(message);
                                        ^
                                        "%s", 
3 warnings generated.

• deprecated-register (C++17)

	clang++ -DHAVE_CONFIG_H -I. -I..  -I../include "-DRESDIR=\"/opt/local/share/dosbox-x\"" -Wno-int-to-void-pointer-cast   -Wno-address-of-packed-member   -Wno-format-zero-length   -Wno-missing-field-initializers   -Wno-strict-aliasing   -Wno-implicit-fallthrough   -Wno-deprecated-declarations   -Wconversion-null   -Wsign-promo   -pedantic   -Wunused   -Wextra   -Wall   -I/opt/local/include -I/opt/local/include/SDL2 -D_THREAD_SAFE -I/opt/local/include/freetype2 -I/opt/local/include/libpng16 -I/opt/local/include -I/opt/local/include  -g -std=c++11  -O2 -msse  -Wall   -Wextra   -Wunused   -pedantic   -Wsign-promo   -Wconversion-null   -Wno-deprecated-declarations   -Wno-implicit-fallthrough   -Wno-strict-aliasing   -Wno-missing-field-initializers   -Wno-format-zero-length   -Wno-address-of-packed-member   -Wno-int-to-void-pointer-cast   -MT dosbox.o -MD -MP -MF $depbase.Tpo -c -o dosbox.o dosbox.cpp &&\
	mv -f $depbase.Tpo $depbase.Po
In file included from dosbox.cpp:83:
In file included from ../vs2015/zlib/contrib/minizip/zip.c:186:
../vs2015/zlib/contrib/minizip/crypt.h:54:7: warning: 'register' storage class specifier is deprecated and incompatible with C++17 [-Wdeprecated-register]
      register int keyshift = (int)((*(pkeys+1)) >> 24);
      ^~~~~~~~~
1 warning generated.

• and a few unused functions:

	clang++ -DHAVE_CONFIG_H -I. -I../..  -I../../include -Wno-int-to-void-pointer-cast   -Wno-address-of-packed-member   -Wno-format-zero-length   -Wno-missing-field-initializers   -Wno-strict-aliasing   -Wno-implicit-fallthrough   -Wno-deprecated-declarations   -Wconversion-null   -Wsign-promo   -pedantic   -Wunused   -Wextra   -Wall   -I/opt/local/include -I/opt/local/include/SDL2 -D_THREAD_SAFE -I/opt/local/include/freetype2 -I/opt/local/include/libpng16 -I/opt/local/include -I/opt/local/include  -g -std=c++11  -O2 -msse  -Wall   -Wextra   -Wunused   -pedantic   -Wsign-promo   -Wconversion-null   -Wno-deprecated-declarations   -Wno-implicit-fallthrough   -Wno-strict-aliasing   -Wno-missing-field-initializers   -Wno-format-zero-length   -Wno-address-of-packed-member   -Wno-int-to-void-pointer-cast   -MT cdrom_image.o -MD -MP -MF $depbase.Tpo -c -o cdrom_image.o cdrom_image.cpp &&\
	mv -f $depbase.Tpo $depbase.Po
In file included from cdrom_image.cpp:47:
In file included from ../../src/libs/decoders/mp3.cpp:34:
./../libs/decoders/dr_mp3.h:2432:27: warning: unused function 'drmp3_mix_f32' [-Wunused-function]
static DRMP3_INLINE float drmp3_mix_f32(float x, float y, float a)
                          ^
./../libs/decoders/dr_mp3.h:2436:27: warning: unused function 'drmp3_mix_f32_fast' [-Wunused-function]
static DRMP3_INLINE float drmp3_mix_f32_fast(float x, float y, float a)
                          ^
./../libs/decoders/dr_mp3.h:2448:34: warning: unused function 'drmp3_gcf_u32' [-Wunused-function]
static DRMP3_INLINE drmp3_uint32 drmp3_gcf_u32(drmp3_uint32 a, drmp3_uint32 b)
                                 ^
./../libs/decoders/dr_mp3.h:2470:28: warning: unused function 'drmp3_exp' [-Wunused-function]
static DRMP3_INLINE double drmp3_exp(double x)
                           ^
./../libs/decoders/dr_mp3.h:2476:28: warning: unused function 'drmp3_cos' [-Wunused-function]
static DRMP3_INLINE double drmp3_cos(double x)
                           ^
5 warnings generated.

	clang++ -DHAVE_CONFIG_H -I. -I../../..  -I../../../include -Wno-int-to-void-pointer-cast   -Wno-address-of-packed-member   -Wno-format-zero-length   -Wno-missing-field-initializers   -Wno-strict-aliasing   -Wno-implicit-fallthrough   -Wno-deprecated-declarations   -Wconversion-null   -Wsign-promo   -pedantic   -Wunused   -Wextra   -Wall   -I/opt/local/include -I/opt/local/include/SDL2 -D_THREAD_SAFE -I/opt/local/include/freetype2 -I/opt/local/include/libpng16 -I/opt/local/include -I/opt/local/include  -g -std=c++11  -O2 -msse  -Wall   -Wextra   -Wunused   -pedantic   -Wsign-promo   -Wconversion-null   -Wno-deprecated-declarations   -Wno-implicit-fallthrough   -Wno-strict-aliasing   -Wno-missing-field-initializers   -Wno-format-zero-length   -Wno-address-of-packed-member   -Wno-int-to-void-pointer-cast   -MT ymf262.o -MD -MP -MF $depbase.Tpo -c -o ymf262.o ymf262.cpp &&\
	mv -f $depbase.Tpo $depbase.Po
ymf262.cpp:684:20: warning: unused function 'OPL3_STATUSMASK_SET' [-Wunused-function]
static inline void OPL3_STATUSMASK_SET(OPL3 *chip,int flag)
                   ^
1 warning generated.

Environment (please complete the following information):

• macOS
• DOSBox-X release 0.83.3