Nico Rieck: Currently _MSC_VER and _WIN32 are used to guard code which is

MSVC-specific, MSVCRT-specific, or Windows-specific. Because Clang can
also define _MSC_VER, and MSVCRT is not necessarily the only C runtime,
these macros should not be used interchangeably.

This patch divides all Windows-related bits into the aforementioned
categories. Two new macros are introduced:

- _LIBCPP_MSVC: Defined when compiling with MSVC. Detected using
  _MSC_VER, excluding Clang.
- _LIBCPP_MSVCRT: Defined when using the Microsoft CRT. This is the default
   when _WIN32 is defined.

This leaves _WIN32 for code using the Windows API.

This also corrects the spelling of _LIBCP_HAS_IS_BASE_OF to _LIBCPP_HAS_IS_BASE_OF.

Nico, please prepare a patch for CREDITS.TXT, thanks.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@187593 91177308-0d34-0410-b5e6-96231b3b80d8

include/support/win32/support.h

@@ -30,7 +30,7 @@ size_t wcsnrtombs( char *__restrict dst, const wchar_t **__restrict src,
                    size_t nwc, size_t len, mbstate_t *__restrict ps );
 }
 
-#if defined(_MSC_VER)
+#if defined(_LIBCPP_MSVCRT)
 #define snprintf _snprintf
 #include <xlocinfo.h>
 #define atoll _atoi64
@@ -109,6 +109,6 @@ _LIBCPP_ALWAYS_INLINE int __builtin_clzll( unsigned long long x )
     return static_cast<int>(r);
 }
 #endif // !__clang__
-#endif // _MSC_VER
+#endif // _LIBCPP_MSVCRT
 
 #endif // _LIBCPP_SUPPORT_WIN32_SUPPORT_H