patch 8.1.1978: the eval.c file is too big

Problem:    The eval.c file is too big.
Solution:   Move filter() and map() to list.c.

src/version.c

@@ -761,6 +761,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1978,
 /**/
     1977,
 /**/