in short we now record whenever the slave I/O thread ignores a master's event because of its server id,
and use this info in the slave SQL thread to advance Exec_master_log_pos. Because if we
do not, this variable stays at the position of the last executed event, i.e. the last *non-ignored*
executed one, which may not be the last of the master's binlog (and so the slave *looks* behind
the master though it's data-wise it's not).


mysql-test/t/rpl_dual_pos_advance-master.opt:
  empty; its goal is just to trigger a server restart after running the test,
  so that the master forgets that it was a slave (otherwise it affects the following tests).
sql/log.cc:
  No more default arguments for Rotate_log_event constructor.
  MYSQL_LOG::appendv() is now called without mutex.
sql/log_event.cc:
  Moving one Rotate_log_event constructor from log_event.h. Support for on-demand choice of
  duplicating the string argument of the constructor or not (because there now are needs for both
  alternatives, see slave.cc).
sql/log_event.h:
  We now have a case where a Rotate_log_event is executed by the slave SQL thread while
  not being in the relay log, so it needs to pretend its length is 0: a ZERO_LEN flag for that;
  a flag DUP_NAME (replaces "bool alloced") to be able to choose if we want the constructor
  to duplicate the string argument or not.
sql/slave.cc:
  A comment for BUG#13861 (to be fixed). llstr() instead of %ld as the number is ulonglong.
  mi->rli becomes rli in some places.
  Fix for BUG#13023:
  - in the slave I/O thread, whenever we ignore an event because of its server id we update
  a couple of coordinates in memory
  - in the slave SQL thread, whenever we bump into the end of the latest relay log, we check
  this couple of coordinates to see if we should advance our Exec_master_log_pos.
  - when the slave I/O thread terminates it saves these in-memory coordinates into a Rotate event
  in the relay log, so that they are durable.
sql/slave.h:
  A couple of coordinates in RELAY_LOG_INFO to keep track of the last ignored events received
  by the slave I/O thread (ignored because of the server id).
mysql-test/r/rpl_dual_pos_advance.result:
  New BitKeeper file ``mysql-test/r/rpl_dual_pos_advance.result''
mysql-test/t/rpl_dual_pos_advance.test:
  Test for BUG#13023 (with a part, disabled, to test BUG#13861 when I fix it).
  Before the fix, this test used to hang.