Fix for BUG#6522 "Replication fails due to a rolled back transaction in the binlog"

When we are writing a transaction to the binlog, we log BEGIN/COMMIT with zero error code.
Example: all statements of trans succeeded, connection lost and so implicit rollback:
we don't want ER_NET* errors to be logged in the BEGIN/ROLLBACK events, while statement
events have 0. If there was really a serious error code, it's already in the statement events.


sql/log.cc:
  When we write the cached binlog segment to disk binlog at COMMIT/ROLLBACK time:
  imagine this is rollback due to net timeout, after all statements of
  the transaction succeeded. Then we want a zero-error code in BEGIN.
  In other words, if there was a really serious error code it's already
  in the transaction's statement events.
sql/sql_table.cc:
  out of date comment

sql/log.cc

@@ -1370,6 +1370,14 @@ bool MYSQL_LOG::write(THD *thd, IO_CACHE *cache, bool commit_or_rollback)
     */
     {
       Query_log_event qinfo(thd, "BEGIN", 5, TRUE);
+      /*
+        Imagine this is rollback due to net timeout, after all statements of
+        the transaction succeeded. Then we want a zero-error code in BEGIN.
+        In other words, if there was a really serious error code it's already
+        in the statement's events.
+        This is safer than thd->clear_error() against kills at shutdown.
+      */
+      qinfo.error_code= 0;
       /*
         Now this Query_log_event has artificial log_pos 0. It must be adjusted
         to reflect the real position in the log. Not doing it would confuse the
@@ -1403,6 +1411,7 @@ bool MYSQL_LOG::write(THD *thd, IO_CACHE *cache, bool commit_or_rollback)
                             commit_or_rollback ? "COMMIT" : "ROLLBACK",
                             commit_or_rollback ? 6        : 8, 
                             TRUE);
+      qinfo.error_code= 0;
       qinfo.set_log_pos(this);
       if (qinfo.write(&log_file) || flush_io_cache(&log_file))
 	goto err;

sql/sql_table.cc

@@ -911,7 +911,6 @@ TABLE *create_table_from_items(THD *thd, HA_CREATE_INFO *create_info,
   }
   table->file->extra(HA_EXTRA_WRITE_CACHE);
   DBUG_RETURN(table);
-  /* Note that leaving the function resets binlogging properties */
 }