WL#834: Extend MySQLdump to allow consistent with replication dump for all table types

Status: Un-Assigned   —   Priority: Medium

This is combined task it needs both server and client support to function.

Basically the goal is to add an option to MySQLdump to provide consistent backup,
synced with position in binary log  independent on table types existing.

In general we should work the following way:
- Atomic way do the following:
   - lock all tables which does not allow consistent snapshot
   - start transaction with new snapshot associated to it
   - get current binary log position

Afterwards we can perform normal mysqldump operation  by dumping tables content 
as SQL files or LOAD DATA source files.

Some possible tweaks:
 - we can implement READ CONSISTENT lock type which would work for all tables
and  just do not lock table for Innodb table. We can later reuse it as soon as
MyISAM will support HotBackup.
 - we can add "UNLOCK TABLE X" statement to unlock table as soon as we have done
with it.
 - We should add support for MERGE tables. Content should not be dumped for
these tables only CREATE TABLE unless explitely wanted.
 - We should extend mysqldump to be able to support --tab while dumping multiple