aways from zero, instead of rounding towards zero.

It should make test_asyncio more reliable, especially test_timeout_rounding() test.

Nowadays it is likely that people will have Sphinx installed,
and if not, they will know how to install it.

This also simplifies life a lot for distribution packagers,
who typically do not want the doc build process to connect
to external web resources.

Patch by Vajrasky Kok.

- now also allows POSIX installation with SSL/TLS missing
- a goal for pip 1.6 is to allow local use without SSL/TLS

regression: don't clear anymore the state of Python threads early during the
Python shutdown.