patch 8.1.1943: more code can be moved to evalvars.c

Problem:    More code can be moved to evalvars.c.
Solution:   Move it, clean up comments.  Also move some window related
            functions to window.c. (Yegappan Lakshmanan, closes #4874)

src/version.c

@@ -761,6 +761,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1943,
 /**/
     1942,
 /**/