mysql-test/mysql-test-run.pl:
  1. Improved description of option user=USER
  2. Bug fix 
     The storage place of the old, to be removed <test case>.reject file is the 'r' subdirectory of the test suite.
  3. New option "start-dirty" which is 
     - per functionality a "start-and-exit" without an initiation
     - a convenient method to (re)start an existing database. 
       So a following
            ./mysql-test-run.pl --extern ......
       will meet a server running with the default ports and sockets according to our test environment.
     This option is useful for analyzing bugs and  WL#2520 Upgrade/Downgrade Test Plan .