mysql-test/lib/My/Options.pm:
  My::Options::is_set() now matches both option names and values!
mysql-test/lib/mtr_cases.pm:
  1. don't merge --plugin-load here, it's too early
  2. don't skip combinations that set --plugin-load just because the test needs another --plugin-load.
     Skip *only* if test's --plugin-load matches *exactly* --plugin-load of one of the combinations.
  3. if skipping all combinations but one, still assign the test to the combination
mysql-test/mysql-test-run.pl:
  1. remove dead code - don't set variables that aren't used.
  2. bugfix: allow one-letter combination names
  3. in the command line, merge all --plugin-load options in one
storage/federated/ha_federated.cc:
  bugfix: garbage character in the generated SELECT query