Bug#12713 "Error in a stored function called from a SELECT doesn't

cause ROLLBACK of statement", part 1. Review fixes.

Do not send OK/EOF packets to the client until we reached the end of 
the current statement.
This is a consolidation, to keep the functionality that is shared by all 
SQL statements in one place in the server.
Currently this functionality includes:
- close_thread_tables()
- log_slow_statement().

After this patch and the subsequent patch for Bug#12713, it shall also include:
- ha_autocommit_or_rollback()
- net_end_statement()
- query_cache_end_of_result().

In future it may also include:
- mysql_reset_thd_for_next_command().

sql/opt_sum.cc

@@ -170,6 +170,7 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds)
       if(error)
       {
         tl->table->file->print_error(error, MYF(0));
+        tl->table->in_use->fatal_error();
         return error;
       }
       count*= tl->table->file->stats.records;
@@ -418,6 +419,7 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds)
 	      return HA_ERR_KEY_NOT_FOUND;	     // No rows matching WHERE
 	    /* HA_ERR_LOCK_DEADLOCK or some other error */
  	    table->file->print_error(error, MYF(0));
+            table->in_use->fatal_error();
             return(error);
 	  }
           removed_tables|= table->map;