bpo-37957: Allow regrtest to receive a file with test (and subtests) to ignore (GH-16989)

When building Python in some uncommon platforms there are some known tests that will fail. Right now, the test suite has the ability to ignore entire tests using the -x option and to receive a filter file using the --matchfile filter. The problem with the --matchfile option is that it receives a file with patterns to accept and when you want to ignore a couple of tests and subtests, is too cumbersome to lists ALL tests that are not the ones that you want to accept and he problem with -x is that is not easy to ignore just a subtests that fail and the whole test needs to be ignored.

For these reasons, add a new option to allow to ignore a list of test and subtests for these situations.
diff --git a/Lib/test/libregrtest/main.py b/Lib/test/libregrtest/main.py
index 76ad335..1de51b7 100644
--- a/Lib/test/libregrtest/main.py
+++ b/Lib/test/libregrtest/main.py
@@ -287,7 +287,7 @@
 
     def list_cases(self):
         support.verbose = False
-        support.set_match_tests(self.ns.match_tests)
+        support.set_match_tests(self.ns.match_tests, self.ns.ignore_tests)
 
         for test_name in self.selected:
             abstest = get_abs_module(self.ns, test_name)