py3-related fixes

thanks to @fantix for original patch.

Thanks to @fantix for original patch.

and ignore gevent/util_py2.py

based on #362 by @fantix

Added __bool__ for PY3 next to __nonzero__.

Remove test_support.py

Port gevent vfd to win64

Since long on win64 is 32-bit it cannot hold all possible
SOCKET handle values, making it theoretically possible to
get an exception "OverflowError: Python int too large to
convert to C long" if socket handles become too big. Now
on win64 it properly uses PY_LONG_LONG.

Refs #38, fix pywsgi headers issue in PY3

Ignore sys.exc_clear() for PY3.

Fix indexing exceptions (ex[0]) by using args (ex.args[0]), refs #38

Refs #38, fixed renamed symbols in PY3

Fix links for examples (docs gevent servers)

Fixed exec, refs #38.

Replaced execfile() with exec(open().read()) in gevent/monkey.py.

upgrade libev to 4.15

This should fix #361.

not needed since 2.5 is not supported anymore.

- do not swallow syntax errors
- make pyflakes.py py3-compatible #38
- run using specific version of python (previously pyflakes from the default python
  was used, which caused it to ignore py3-specific and py2.6-specific syntax errors