Mark cs_* as thread local to avoid race condition in multithreads

[wtdcode]

Per @trufae reported,

=================================================================
==251167==ERROR: AddressSanitizer: odr-violation (0x7f5cd9115f40):
  [1] size=8 'cs_vsnprintf' cs.c:299:16
  [2] size=8 'cs_vsnprintf' cs.c:299:16
These globals were registered at these points:
  [1]:
    #0 0x7f5ce2a20938 in __asan_register_globals ../../../../src/libsanitizer/asan/asan_globals.cpp:341
    #1 0x7f5cd5fbc712 in _sub_I_00099_1 (/usr/local/lib/libr_anal.so+0x3260712)
    #2 0x7f5ce3401b99 in call_init /build/glibc-SzIz7B/glibc-2.31/elf/dl-init.c:72

  [2]:
    #0 0x7f5ce2a20938 in __asan_register_globals ../../../../src/libsanitizer/asan/asan_globals.cpp:341
    #1 0x7f5cde789b44 in _sub_I_00099_1 (/usr/local/lib/libr_asm.so+0x103db44)
    #2 0x7f5ce3401b99 in call_init /build/glibc-SzIz7B/glibc-2.31/elf/dl-init.c:72

==251167==HINT: if you don't care about these errors you may set ASAN_OPTIONS=detect_odr_violation=0
SUMMARY: AddressSanitizer: odr-violation: global 'cs_vsnprintf' at cs.c:299:16
==251167==ABORTING

This PR marks cs_* variables as thread_local to avoid race access in multiple threads. For platforms that don't support thread_local, this PR does nothing.

[kabeor]

Great！