Adds deprecation warning for the mysqlbinlog options
--base64-output=always and --base64-output.
A warning is printed when the flags are used,
and also when running mysqlbinlog --help.


client/mysqlbinlog.cc:
  Give a warning for --base64-output=always and --base64-output,
  and print warning in mysqlbinlog --help.
mysql-test/r/mysqlbinlog.result:
  updated result file
mysql-test/t/mysqlbinlog.test:
  Test that mysqlbinlog --base64-output=always gives a warning.