inspect.getfile: Don't crash on classes without '__module__' attribute #20372

Some classes defined in C may not have the '__module__' attribute, so
we now handle this case to avoid having unexepected AttributeError.
doc/inspect: Clarify docs for __defaults__, add docs for __kwdefaults__ #20380
inspect.signature: Use '/' to separate positional-only parameters from
the rest in Signature.__str__. #20356
Issue #19456: ntpath.join() now joins relative paths correctly when a drive
is present.
Issue #19456: ntpath.join() now joins relative paths correctly when a drive
is present.
asyncio doc: subprocess_exec/subprocess_shell are not available on Windows
inspect.signature: Add support for 'functools.partialmethod' #20223
asyncio: remove temporary aliases
inspect.signature: Support classes without user-defined __init__/__new__ #20308
NEWS: Add few missing news items
asyncio doc: list Windows and Mac OS X limitations and explain how to work
around them
Fix doc reference to OS X 10.9 Mavericks.