patch 8.1.0941: macros for MS-Windows are inconsistent

Problem:    Macros for MS-Windows are inconsistent, using "32", "3264 and
            others.
Solution:   Use MSWIN for all MS-Windows builds.  Use FEAT_GUI_MSWIN for the
            GUI build. (Hirohito Higashi, closes #3932)
diff --git a/src/blowfish.c b/src/blowfish.c
index 8ca0e28..7bc3e31 100644
--- a/src/blowfish.c
+++ b/src/blowfish.c
@@ -34,7 +34,7 @@
     char_u   uc[8];
 } block8;
 
-#if defined(WIN3264)
+#if defined(MSWIN)
   /* MS-Windows is always little endian */
 #else
 # ifdef HAVE_CONFIG_H