patch 8.1.0743: giving error messages is not flexible

Problem:    Giving error messages is not flexible.
Solution:   Add semsg().  Change argument from "char_u *" to "char *", also
            for msg() and get rid of most MSG macros. (Ozaki Kiichi, closes
            #3302)  Also make emsg() accept a "char *" argument.  Get rid of
            an enormous number of type casts.
diff --git a/src/hashtab.c b/src/hashtab.c
index 4bf41e0..bc86a07 100644
--- a/src/hashtab.c
+++ b/src/hashtab.c
@@ -334,9 +334,9 @@
 
 #ifdef HT_DEBUG
     if (ht->ht_used > ht->ht_filled)
-	EMSG("hash_may_resize(): more used than filled");
+	emsg("hash_may_resize(): more used than filled");
     if (ht->ht_filled >= ht->ht_mask + 1)
-	EMSG("hash_may_resize(): table completely filled");
+	emsg("hash_may_resize(): table completely filled");
 #endif
 
     if (minitems == 0)