Split <stdio.h> out of <cstdio>.

As with <stddef.h>, skip our custom header if __need_FILE or __need___FILE is defined.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@249798 91177308-0d34-0410-b5e6-96231b3b80d8

include/cstdio

@@ -103,16 +103,6 @@ void perror(const char* s);
 #pragma GCC system_header
 #endif
 
-// snprintf
-#if defined(_LIBCPP_MSVCRT)
-#include "support/win32/support.h"
-#endif
-
-#undef getc
-#undef putc
-#undef clearerr
-#undef feof
-#undef ferror
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 using ::FILE;