Issue #19965: Make sure that Python-ast.h is properly taken into account in the
makefile.
Issue #19912: Fixed numerous bugs in ntpath.splitunc().

* splitunc() no more returns illegal result for paths with redundant slashes.
* splitunc() now correctly processes the u'İ' character
  (U+0130, LATIN CAPITAL LETTER I WITH DOT ABOVE).
* Added new tests for splitunc().
Merge heads
Issue #19987: Re-write test_alias_fallback in test_winsound to have two
acceptable outcomes: success or RuntimeError.  Without being able to
actually hear whether a sound was played, either one could be right, but
any other error would be a failure.
Removed old implementation of ntpath.splitunc() (issue #19912).