patch 8.2.4038: various code not used when features are disabled

Problem:    Various code not used when features are disabled.
Solution:   Add #ifdefs. (Dominique Pellé, closes #9491)

src/userfunc.c

@@ -39,6 +39,7 @@ func_init()
     hash_init(&func_hashtab);
 }
 
+#if defined(FEAT_PROFILE) || defined(PROTO)
 /*
  * Return the function hash table
  */
@@ -47,6 +48,7 @@ func_tbl_get(void)
 {
     return &func_hashtab;
 }
+#endif
 
 /*
  * Get one function argument.