Post review changes
the --read-only option is not enforced for the slave thread in replication, or for the SUPER user.


sql/handler.cc:
  Post review changes
  Allowing writes for the slave thread or for SUPER, in read-only mode
sql/lock.cc:
  Post review changes
  Allowing writes for the slave thread or for SUPER, in read-only mode
mysql-test/r/rpl_read_only.result:
  New test
mysql-test/t/rpl_read_only-slave.opt:
  New test
mysql-test/t/rpl_read_only.test:
  New test