updated for version 7.3.727
Problem:    Can't always find Win32.mak when building GvimExt.
Solution:   Use same mechanism as in Make_mvc.mak. (Cade Foster)
diff --git a/src/GvimExt/Makefile b/src/GvimExt/Makefile
index 2488025..5c598c1 100644
--- a/src/GvimExt/Makefile
+++ b/src/GvimExt/Makefile
@@ -10,7 +10,11 @@
 NODEBUG = 1
 !endif
 
-!include <win32.mak>
+!ifdef SDK_INCLUDE_DIR
+!include $(SDK_INCLUDE_DIR)\Win32.mak
+!else
+!include <Win32.mak>
+!endif
 
 all: gvimext.dll