patch 8.1.1076: file for Insert mode is much too big

Problem:    File for Insert mode is much too big.
Solution:   Split off the code for Insert completion. (Yegappan Lakshmanan,
            closes #4044)

src/misc2.c

@@ -1130,6 +1130,7 @@ free_all_mem(void)
     free_search_patterns();
     free_old_sub();
     free_last_insert();
+    free_insexpand_stuff();
     free_prev_shellcmd();
     free_regexp_stuff();
     free_tag_stuff();