patch 7.4.1980

Problem:    'errorformat' is parsed for every call to ":caddexpr".  Can't add
            to two location lists asynchronously.
Solution:   Keep the previously parsed data when appropriate. (mostly by
            Yegappan Lakshmanan)

src/version.c

@@ -758,6 +758,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1980,
 /**/
     1979,
 /**/