Add astyle function to the supplied pre-commit hook script

It's a bit annoying (at least to me) when the head revision is not astyled properly.
When before committing you call `run_astyle.bat` and it results in getting diffs in seemingly random files (this hook fixes it), or the staged files getting seemingly random diffs (this hook should diminish such occurrences).
Should be pretty useful to both the people with commit rights and random contributors.
It supersedes `checkyear.sh`.

By the way, maybe it's better to rename `contrib` folder to `tools` or something? The current name is quite misleading.

Status: incomplete

To be done:
 - [x] Implement a pre-push hook
 - [x] Wait for msysGit-1.8.2 to be released to test the pre-push hook