Attached pull request adds the --matchfile option to regrtest.
    
* Add a new option taking a filename to get a list of test names to filter tests.
* support.match_tests becomes a list.
* Modify run_unittest() to accept to match the whole test identifier, not just a part of a test identifier.
   
For example, the following command only runs test_default_timeout() of the BarrierTests class of test_threading:
    
$ ./python -m test -v test_threading -m test.test_threading.BarrierTests.test_default_timeout