Fix that uninstaller isn't found on 64-bit Windows.

src/dosinst.h

@@ -83,6 +83,14 @@ char *searchpath(char *name);
 # define TRUE 1
 #endif
 
+/*
+ * Modern way of creating registry entries, also works on 64 bit windows when
+ * compiled as a 32 bit program.
+ */
+# ifndef KEY_WOW64_64KEY
+#  define KEY_WOW64_64KEY 0x0100
+# endif
+
 #define VIM_STARTMENU "Programs\\Vim " VIM_VERSION_SHORT
 
 int	interactive;		/* non-zero when running interactively */