patch 9.0.1390: FOR_ALL_ macros are defined in an unexpected file

Problem:    FOR_ALL_ macros are defined in an unexpected file.
Solution:   Move FOR_ALL_ macros to macros.h.  Add FOR_ALL_HASHTAB_ITEMS.
            (Yegappan Lakshmanan, closes #12109)
diff --git a/src/session.c b/src/session.c
index a34eedf..e39ce4d 100644
--- a/src/session.c
+++ b/src/session.c
@@ -543,7 +543,7 @@
     char_u	*p, *t;
 
     todo = (int)gvht->ht_used;
-    for (hi = gvht->ht_array; todo > 0; ++hi)
+    FOR_ALL_HASHTAB_ITEMS(gvht, hi, todo)
     {
 	if (!HASHITEM_EMPTY(hi))
 	{