patch 8.1.1414: alloc() returning "char_u *" causes a lot of type casts

Problem:    Alloc() returning "char_u *" causes a lot of type casts.
Solution:   Have it return "void *". (Mike Williams)  Define ALLOC_ONE() to
            check the simple allocations.
diff --git a/src/memfile_test.c b/src/memfile_test.c
index 0fa1e14..8408498 100644
--- a/src/memfile_test.c
+++ b/src/memfile_test.c
@@ -67,7 +67,7 @@
 	assert(mf_hash_find(&ht, key) == NULL);
 
 	/* allocate and add new item */
-	item = (mf_hashitem_T *)lalloc_clear(sizeof(mf_hashtab_T), FALSE);
+	item = LALLOC_CLEAR_ONE(mf_hashtab_T);
 	assert(item != NULL);
 	item->mhi_key = key;
 	mf_hash_add_item(&ht, item);