patch 7.4.1109

Problem:    MS-Windows doesn't have rmdir().
Solution:   Add mch_rmdir().

src/version.c

@@ -741,6 +741,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1109,
 /**/
     1108,
 /**/