When using -R, lots of "*** DocTestRunner.merge:" nuisance messages

appear.  Get rid of them by nuking doctest's default DocTestRunner
instance as part of cleanup().  Also cleanup() before running the
first test repetition (the test was run once before we get into
the -R branch).

Lib/test/regrtest.py

@@ -520,7 +520,7 @@ def runtest(test, generate, verbose, quiet, testdir=None, huntrleaks=False):
                 import gc
                 def cleanup():
                     import _strptime, linecache, warnings, dircache
-                    import urlparse, urllib, urllib2, mimetypes
+                    import urlparse, urllib, urllib2, mimetypes, doctest
                     from distutils.dir_util import _path_created
                     _path_created.clear()
                     warnings.filters[:] = fs
@@ -537,6 +537,7 @@ def runtest(test, generate, verbose, quiet, testdir=None, huntrleaks=False):
                     dircache.reset()
                     linecache.clearcache()
                     mimetypes._default_mime_types()
+                    doctest.master = None
                 if indirect_test:
                     def run_the_test():
                         indirect_test()
@@ -548,6 +549,7 @@ def runtest(test, generate, verbose, quiet, testdir=None, huntrleaks=False):
                 print >> sys.stderr, "beginning", repcount, "repetitions"
                 print >> sys.stderr, \
                       ("1234567890"*(repcount//10 + 1))[:repcount]
+                cleanup()
                 for i in range(repcount):
                     rc = sys.gettotalrefcount()
                     run_the_test()