some work on type hint stubs

[Kyle Altendorf]

Hi Phil,

There's been some work over in PyQt5-stubs [0] recently.  It is now 
passing mypy --strict (with 180 reviewed ignores) and we are working 
through the complaints from stubtest (mostly enumeration __new__ 
signatures are left).  Not that automated generic checks catch 
everything, but they are pieces of the puzzle.  Perhaps this work could 
be useful as a reference for some changes to the official stub 
generation.  If you would be interested in any help enhancing the 
official stubs, let us know how.

Cheers,
-kyle


[0] https://github.com/stlehmann/PyQt5-stubs