patch 8.1.0037: cannot easily append lines to another buffer

Problem:    Cannot easily append lines to another buffer.
Solution:   Add appendbufline().

src/version.c

@@ -761,6 +761,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    37,
 /**/
     36,
 /**/