patch 7.4.1438

Problem:    Can't get buffer number of a channel.
Solution:   Add ch_getbufnr().

src/version.c

@@ -743,6 +743,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1438,
 /**/
     1437,
 /**/