py-gevent: updated to 1.3.7

1.3.7:
- Formatting run info no longer includes gevent.local.local
  objects that have no value in the greenlet.
- Fixed negative length in pywsgi's Input read functions for non chunked body.
- Upgrade libuv from 1.22.0 to 1.23.2.
- Fix opening files in text mode in CPython 2 on Windows by patching
  libuv.

(adam)