[VCRUNTIME] Move compiler runtime headers into their own folder

These headers come with the MS compiler. Some of them are standard, like emmintrin.h, others are MS specific like crtdefs.h
This separation will allow using MS CRT headers. Eventually it can allow compiling with the compilers' runtime headers.

sdk/include/vcruntime/varargs.h

@@ -0,0 +1,12 @@
+/**
+ * This file has no copyright assigned and is placed in the Public Domain.
+ * This file is part of the w64 mingw-runtime package.
+ * No warranty is given; refer to the file DISCLAIMER within this package.
+ */
+#ifndef _VARARGS_H
+#define _VARARGS_H
+
+#error "GCC no longer implements <varargs.h>."
+#error "Revise your code to use <stdarg.h>."
+
+#endif