[X86] Add __crc32b/__crc32w/__crc32d/__crc32q intrinsics to match gcc and icc.

[craig.topper]

Summary

gcc has these intrinsics in ia32intrin.h as well. And icc implements them
though they aren't documented in the Intel Intrinsics Guide.

[craig.topper]

Add the test file that I forgot to git add before running arcanist

[RKSimon]

LGTM with one minor (doxygen desciptions)

lib/Headers/ia32intrin.h

58

Please can you copy the doxygen comments from smmintrin.h (_mm_crc32_u8 etc.)?

lib/Headers/ia32intrin.h

 
 static __inline__ void __attribute__((__always_inline__, __nodebug__))
 __writeeflags(unsigned int __f)
 {
   __builtin_ia32_writeeflags_u32(__f);
 }
 #endif /* !__x86_64__ */
 
+static __inline__ unsigned int __attribute__((__always_inline__, __nodebug__, __target__("sse4.2")))
+__crc32b(unsigned int __C, unsigned char __D)
+{
+  return __builtin_ia32_crc32qi(__C, __D);
+}
+
+static __inline__ unsigned int __attribute__((__always_inline__, __nodebug__, __target__("sse4.2")))
+__crc32w(unsigned int __C, unsigned short __D)
+{
+  return __builtin_ia32_crc32hi(__C, __D);
+}
+
+static __inline__ unsigned int __attribute__((__always_inline__, __nodebug__, __target__("sse4.2")))
+__crc32d(unsigned int __C, unsigned int __D)
+{
+  return __builtin_ia32_crc32si(__C, __D);
+}
+
+#ifdef __x86_64__
+static __inline__ unsigned long long __attribute__((__always_inline__, __nodebug__, __target__("sse4.2")))
+__crc32q(unsigned long long __C, unsigned long long __D)
+{
+  return __builtin_ia32_crc32di(__C, __D);
+}
+#endif /* __x86_64__ */
+
 static __inline__ unsigned long long __attribute__((__always_inline__, __nodebug__))
 __rdpmc(int __A) {
   return __builtin_ia32_rdpmc(__A);
 }
 
 /* __rdtscp */
 static __inline__ unsigned long long __attribute__((__always_inline__, __nodebug__))
 __rdtscp(unsigned int *__A) {