Add support for page 1252 encoding

Rdrview is failing to handle pages that use the Windows-1252 encoding:

  #15

Just like GB2312, this encoding is only supported via iconv, not
directly by libxml2. Since iconv conversions need to read files from
disk, initialize the conversion descriptor before setting up the
sandbox.

src/rdrview.c

@@ -769,8 +769,9 @@ static inline void assert_sandbox_works(void)
 }
 #endif /* NDEBUG */
 
-/* Descriptors for the encodings supported via iconv; for now only GB2312 */
+/* Descriptors for the encodings supported via iconv */
 static iconv_t gb2312_cd;
+static iconv_t cp1252_cd;
 
 /**
  * Set up the iconv conversion descriptors to be used by libxml2. This is
@@ -781,6 +782,10 @@ static void init_iconv(void)
 	gb2312_cd = iconv_open("UTF-8", "GB2312");
 	if (gb2312_cd == (iconv_t)(-1))
 		fatal_errno();
+
+	cp1252_cd = iconv_open("UTF-8", "CP1252");
+	if (cp1252_cd == (iconv_t)(-1))
+		fatal_errno();
 }
 
 /**
@@ -789,6 +794,7 @@ static void init_iconv(void)
 static void clean_iconv(void)
 {
 	iconv_close(gb2312_cd);
+	iconv_close(cp1252_cd);
 }
 
 /**