merge 2and3 stubs for select (#1333)

There don't seem to be significant changes between Python 2 and 3. The Python 2
stub was much better, so I mostly built off of it.

stdlib/3/select.pyi

@@ -1,27 +0,0 @@
-# Stubs for select
-
-# NOTE: These are incomplete!
-
-from typing import Any, Tuple, List, Sequence
-
-class error(Exception): ...
-
-POLLIN = 0
-POLLPRI = 0
-POLLOUT = 0
-POLLERR = 0
-POLLHUP = 0
-POLLNVAL = 0
-
-class poll:
-    def __init__(self) -> None: ...
-    def register(self, fd: Any,
-                 eventmask: int = ...) -> None: ...
-    def modify(self, fd: Any, eventmask: int) -> None: ...
-    def unregister(self, fd: Any) -> None: ...
-    def poll(self, timeout: int = ...) -> List[Tuple[int, int]]: ...
-
-def select(rlist: Sequence, wlist: Sequence, xlist: Sequence,
-           timeout: float = ...) -> Tuple[List[Any],
-                                           List[Any],
-                                           List[Any]]: ...