WL6742-Improve InnoDB SELECT COUNT(*) performance by using handler::records()
introduced new functionality in InnoDB.

handler::records can now fail in ways never seen by the server before.

This improved things on the InnoDB side:
kevin.lewis@oracle.com-20130626194505-muocxuem7bd2wiw8
  bug#16802288 - FAILING ASSERTION: PREBUILT->SQL_STAT_START ||
  TRX->STATE == TRX_STATE_ACTIVE
  
  Add error handling for DB_DEADLOCK and DB_LOCK_TABLE_FULL to
  handler::records() for COUNT(*).  Also rollback transaction when
  handler::records receive DB_DEADLOCK, DB_LOCK_TABLE_FULL or
  DB_LOCK_WAIT_TIMEOUT.

However: thd_mark_transaction_to_rollback() isn't enough.
The optimizer needs to abort immediately for the cases mentioned above.

Fix: improve error handling for all calls to handler::records()
Add a new public function ha_records() which does the error checking,
make handler::records() protected.