Define MINGW_W64 and use it instead of _W64

... for detecting MinGW-w64. _W64 is not specific of MinGW-w64, it is
defined for compatibility with MS VC++.

	* nt/inc/ms-w32.h: Define MINGW_W64.

	* admin/CPP-DEFINES: Mention MINGW_W64.

	* nt/addpm.c: Use it.

	* nt/addsection.c: Use it.

	* nt/preprep.c: Use it.

	* src/w32.c: Use MINGW_W64 instead of _W64

	* src/w32term.c: Likewise.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/w32term.c b/src/w32term.c
index 66cdbfaecb0..41ab645f31d 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -100,10 +100,10 @@ extern Cursor w32_load_cursor (LPCTSTR name);
 struct w32_display_info one_w32_display_info;
 struct w32_display_info *x_display_list;
 
-#if _WIN32_WINNT < 0x0500 && !defined(_W64)
+#if _WIN32_WINNT < 0x0500 && !defined(MINGW_W64)
 /* Pre Windows 2000, this was not available, but define it here so
    that Emacs compiled on such a platform will run on newer versions.
-   MinGW64 (_W64) defines these unconditionally, so avoid redefining.  */
+   MinGW64 defines these unconditionally, so avoid redefining.  */
 
 typedef struct tagWCRANGE
 {