Functions signal(), getsignal(), pthread_sigmask(), sigpending(),
sigwait() and valid_signals() were omitted.
If __all__ is not defined all non-builtin functions should have
correct __module__.
add private method to enum to support replacing global constants with Enum members:
- search for candidate constants via supplied filter
- create new enum class and members
- insert enum class and replace constants with members via supplied module name
- replace __reduce_ex__ with function that returns member name, so previous Python versions can unpickle
modify IntEnum classes to use new method
Yilei Yang
Serhiy Storchaka
orlnub123
Antoine Pitrou
Martin Panter
Ethan Furman
Victor Stinner
Giampaolo Rodola'