too slow

 * udp_client.py
 * gevent/subprocess.py

 * doctest

see 5d8dd0fb

Experimental/WIP PyPy support #248

Some tests fail, consult known_failures.py for the list.

stdlib's signal module is not supported. Depends on https://bitbucket.org/cffi/cffi/issue/152/handling-errors-from-signal-handlers-in

On PyPy, sys.exc_info is shared between greenlets apparently https://bugs.pypy.org/issue1743.

based on gevent-on-pypy/pypycore@f04a41c written by Ralf Schmitt and Lucas Clemente Vella with patches from hasenj and Armin Rigo

on PyPy we do not build it; on CPython .so takes priority over .py.

fix _socket3 send/sendall

Fix __slots__ in ssl3

implement list of known failures as a python script

replaced known_failures.txt with known_failures.py

list of known failures as a python script

replaced known_failures.txt with known_failures.py

simpler impl of backdoor.py and few minor changes

'result' into 'thread_result'