Code review comment for lp:~paul-mccullagh/maria/maria-pbxt-rc3

I have made 2 changes to the original proposal:

1. I have improved the bug fix in RN291 (bug #489088). The problem was: [Warning] Plugin 'PBXT' will be forced to shutdown. The bug fix caused a crash under certain circumstances. This has been fixed.

2. I have def'd out the following code (changed ifndef to ifdef):

#ifndef WILL_BE_DELETED_LATER
  /*
    for now, only InnoDB supports 2pc. It means we can always safely
    rollback all pending transactions, without risking inconsistent data
  */
  DBUG_ASSERT(total_ha_2pc == (ulong) opt_bin_log+1); // only InnoDB and binlog
  tc_heuristic_recover= TC_HEURISTIC_RECOVER_ROLLBACK; // forcing ROLLBACK
  info.dry_run=FALSE;
#endif