Add ctypes

[tharvik]

https://docs.python.org/3/library/ctypes.html

It was kinda hard to do, but that should do it.

• _DLL is a local class to allow having a common subtype
• _FuncProto is a fake class to avoid having a too big Union
• I was unable to find a way to typecheck c_int * 3 which should gives an Array

[gvanrossum]

@tharvik Not quite, see #475.

[gvanrossum]

I've temporarily deleted these stubs, see #475 for details.