patch 8.0.1276: key lost when window closed in exit callback

Problem:    Typed key is lost when the terminal window is closed in exit
            callback. (Gabriel Barta)
Solution:   When the current window changes bail out of the wait loop. (closes
            #2302)

src/version.c

@@ -761,6 +761,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1276,
 /**/
     1275,
 /**/