Support for GTID in mysqlbinlog

The mysqlbinlog client program needs to be updated to support GTID.

Here is a suggested list of things to be done:

• The --start-position and --stop-position options should be able to take
  GTID positions; or maybe there should be new --start-gtid and --stop-gtid
  options. Like --start-gtid=0-1-100,1-2-200,2-1-1000.

• A GTID position means the point just after that GTID. So starting from
  GTID 0-1-100 and stopping at GTID 0-1-200, the first GTID output will
  probably be 0-1-101 and the last one 0-1-200. Note that if some domain is
  not specified in the position, it means to start from the begining,
  respectively stop immediately in that domain.

• Starting and stopping GTID should work both with local files, and with
  --read-from-remote-server. For the latter, there are a couple of extra
  things that need doing in the master-slave protocol, see
  get_master_version_and_clock() in sql/slave.cc.

• At the end of the dump, put these statements, to reduce the risk of those session variables incorrectly spilling into subsequent statements run in the same session:

  SET session.server_id = @@global.server_id,

  session.gtid_domain_id=@@global.gtid_domain_id;

  Probably some more things will come up during the work, but this looks like a
  reasonable start.