add explanation comment for use of CAPSTONE_API

Signed-off-by: Satoshi Tanda <tanda.sat@gmail.com>

arch/X86/X86Mapping.c

@@ -2923,6 +2923,9 @@ static struct insn_reg2 insn_regs_intel2[] = {
 
 static struct insn_reg insn_regs_intel_sorted [ARR_SIZE(insn_regs_intel)];
 
+// Explicitly specified calling convention with CAPSTONE_API so that it is always
+// compiled as __cdecl on MSVC and does not cause a compile error even when
+// default calling convention is __stdcall (eg. capstone_static_winkernel project)
 static int CAPSTONE_API regs_cmp(const void *a, const void *b)
 {
 	uint16_t l = ((struct insn_reg *)a)->insn;