gevent.core: loop() and dispatch() now raise IOError if corresponding libevent functions return an error

core.pyx: make it compatible with libevent-1.3 which does not have _EVENT_VERSION nor event_reinit()

Thanks to Litao Wei for finding this out.

add test_queue.py from standard tests to check how good is gevent.queue.Queue a replacement for standard Queue

no good at all, fails miserably

gevent.socket.GreenSocket: use socket from standard _socket for wrapped instance instead of standard socket.py

this only affects Python 2.6, which fixes the imports in modules run by runpy.py

- manually backout "properly interpret maxsize parameter of Queue"
- make Queue(0) behave like a channel, not like infinite queue (that's the difference from the standard Queue)