Replace patches using sed and perl with pure php.

Hi, all.
I've implemented #343. This pull request is a bit large and might have architecutral design issues, so it would be helpful that you could point them out.

The summary of my changes is the following:

* Replace calls of sed and perl oneliners with `preg_replace` function calls.
* Define `PHPBREW_EXPECTED_PHP_DIR` and `PHPBREW_FIXTURES_PHP_DIR` in phpunit.xml.
* Introduces a common interface of patch utility classes.
* Add a new class `RegexpPatch` which replaces a content of files using regexp.
* Add tests for `Apxs2PatchTask`, `Patch64BitSupportTask`, `RegexpPatch`, and `RegexpPatchRule`.
* Add an utility class which provides a way to create temprary files while testing.

Sincerely.
A patch object might want to know the information from the build object, thus we may pass the $build object to it.