Bunch of patches

These patches do:
- Replace fork in specs so that it can run on Windows, JRuby
- Refactor different variants of waiting for the connection socket
- Fix conn.wait_for_notify() and conn.block() on Windows
- Add GVL wrappers to blocking libpq functions
- Add Travis-CI to ruby-pg against PG-9.2.2 and 8.3.22
- Fix specs so that all Travis runs are green

With these patches the specs can finally run on Windows and they all pass on my test system with MRI-1.8.7 and 1.9.3.

Unfortunatelly there is a new issue that you can see on travis: https://travis-ci.org/larskanis/ruby-pg/builds/4335837
It seems to be a GC related issue. Currently I'm not able to reproduce it locally. I'll setup a test
environment analog to travis-ci's at the weekend, to dig deeper into it.

You additionally need to update Manifest.txt, but I'm not sure how you used to generate it.