MdeModulePkg/RegularExpressionDxe: Optimize the code infrastructure

OnigurumaIntrinsics.c is now not used. So the implement of function
'memcpy' is now not., which causes build failure with CLANG9 and
XCODE. I remove OnigurumaIntrinsics.c and move the necessary function
implement to OnigurumaUefiPort.c/h.

Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Hao A Wu <hao.a.wu@intel.com>
Signed-off-by: Shenglei Zhang <shenglei.zhang@intel.com>
Reviewed-by: Jian J Wang <jian.j.wang@intel.com>

MdeModulePkg/Universal/RegularExpressionDxe/OnigurumaUefiPort.h

@@ -96,6 +96,8 @@ int EFIAPI sprintf_s (char *str, size_t sizeOfBuffer, char const *fmt, ...);
 int strlen(const char* str);
 void* malloc(size_t size);
 void* realloc(void *ptr, size_t size);
+void* memcpy (void *dest, const void *src, unsigned int count);
+void* memset (void *dest, char ch, unsigned int count);
 
 #define exit(n) ASSERT(FALSE);