patch 9.1.0027: Vim is missing a foreach() func

Problem:  Vim is missing a foreach() func
Solution: Implement foreach({expr1}, {expr2}) function,
          which applies {expr2} for each item in {expr1}
          without changing it (Ernie Rael)

closes: #12166

Signed-off-by: Ernie Rael <errael@raelity.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/structs.h b/src/structs.h
index 6d77deb..85f440d 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -4879,11 +4879,12 @@
     hashtab_T	sve_hashtab;
 } save_v_event_T;
 
-// Enum used by filter(), map() and mapnew()
+// Enum used by filter(), map(), mapnew() and foreach()
 typedef enum {
     FILTERMAP_FILTER,
     FILTERMAP_MAP,
-    FILTERMAP_MAPNEW
+    FILTERMAP_MAPNEW,
+    FILTERMAP_FOREACH
 } filtermap_T;
 
 // Structure used by switch_win() to pass values to restore_win()