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, 13 insertions, 3 deletions

diff --git a/nt/inc/ms-w32.h b/nt/inc/ms-w32.h
index 8f7c36ab1ee..1d45df743de 100644
--- a/nt/inc/ms-w32.h
+++ b/nt/inc/ms-w32.h
@@ -26,6 +26,16 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include <mingw_time.h>
 
+/* MinGW-w64 gcc does not automotically define a macro for
+   differentiating it fom MinGW gcc. We need to test the presence of
+   __MINGW64_VERSION_MAJOR in _mingw.h: */
+#ifdef __MINGW32__
+# include <_mingw.h>
+# ifdef __MINGW64_VERSION_MAJOR
+#  define MINGW_W64
+# endif
+#endif
+
 /* #undef const */
 
 /* Number of chars of output in the buffer of a stdio stream. */
@@ -139,7 +149,7 @@ extern char *getenv ();
    versions we still support.  MinGW64 defines this to a higher value
    in its system headers, and is not really compatible with values
    lower than 0x0500, so leave it alone.  */
-#ifndef _W64
+#ifndef MINGW_W64
 # define _WIN32_WINNT 0x0400
 #endif
 
@@ -165,7 +175,7 @@ extern char *getenv ();
 
 #ifdef emacs
 
-#ifdef _W64
+#ifdef MINGW_W64
 /* MinGW64 specific stuff.  */
 /* Make sure 'struct timespec' and 'struct timezone' are defined.  */
 #include <sys/types.h>
@@ -368,7 +378,7 @@ typedef int sigset_t;
 typedef int ssize_t;
 #endif
 
-#ifdef _W64     /* MinGW64 */
+#ifdef MINGW_W64
 #ifndef _POSIX
 typedef _sigset_t sigset_t;
 #endif