Bug#25183 (Compiler warnings in the sql directory (GCC 4.1))

Fixed compiler warnings.

In set_var.cc, the code was not properly returning an error code
if close_cached_tables() failed.

In sql_tables.cc, the code was not returning properly an error code
if lock_table_names() failed.

Both cases are bugs, introduced in 5.1 only by recent changes.

sql/set_var.cc

@@ -3904,7 +3904,7 @@ bool sys_var_opt_readonly::update(THD *thd, set_var *var)
     can cause to wait on a read lock, it's required for the client application
     to unlock everything, and acceptable for the server to wait on all locks.
   */
-  if (close_cached_tables(thd, true, NULL, false))
+  if (result= close_cached_tables(thd, true, NULL, false))
     goto end_with_read_lock;
 
   if (result= make_global_read_lock_block_commit(thd))

sql/sql_table.cc

@@ -5406,16 +5406,19 @@ bool mysql_alter_table(THD *thd,char *new_db, char *new_name,
     {
       my_message(ER_LOCK_OR_ACTIVE_TRANSACTION,
                  ER(ER_LOCK_OR_ACTIVE_TRANSACTION), MYF(0));
-      DBUG_RETURN(1);
+      DBUG_RETURN(TRUE);
     }
 
     if (wait_if_global_read_lock(thd,0,1))
-      DBUG_RETURN(1);
+      DBUG_RETURN(TRUE);
     VOID(pthread_mutex_lock(&LOCK_open));
     if (lock_table_names(thd, table_list))
+    {
+      error= TRUE;
       goto view_err;
+    }
     
-    error=0;
+    error= FALSE;
     if (!do_rename(thd, table_list, new_db, new_name, new_name, 1))
     {
       if (mysql_bin_log.is_open())
@@ -5556,6 +5559,10 @@ view_err:
       error=table->file->disable_indexes(HA_KEY_SWITCH_NONUNIQ_SAVE);
       /* COND_refresh will be signaled in close_thread_tables() */
       break;
+    default:
+      DBUG_ASSERT(FALSE);
+      error= 0;
+      break;
     }
     if (error == HA_ERR_WRONG_COMMAND)
     {