[CRT] Introduce corecrt.h

Include this instead of crtdefs.h.
This is for compatibility with MS headers.

sdk/include/crt/corecrt.h

@@ -0,0 +1,25 @@
+
+#pragma once
+
+#include <crtdefs.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef _CRTRESTRICT
+#define _CRTRESTRICT
+#endif
+
+#ifndef DEFINED_localeinfo_struct
+typedef struct localeinfo_struct
+{
+    pthreadlocinfo locinfo;
+    pthreadmbcinfo mbcinfo;
+} _locale_tstruct, *_locale_t;
+#define DEFINED_localeinfo_struct 1
+#endif
+
+#ifdef __cplusplus
+} // extern "C"
+#endif