patch 7.4.1691

Problem:    When switching to a new buffer and an autocommand applies syntax
            highlighting an ml_get error may occur.
Solution:   Check "syn_buf" against the buffer in the window. (Alexander von
            Buddenbrock, closes #676)

src/version.c

@@ -748,6 +748,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1691,
 /**/
     1690,
 /**/