New formula: GCC 4.3.

* Track latest GCC 4.3 release.
* Adapt patches from macports.
* Use host triplets for build.
* Use '--datadir' and '--mandir' as datarootdir was not supported yet.
* Don't unset __GLIBCXX_DEBUG* as original bug didn't actually do that.
* Use `uname -m` to detect architecture.

EDIT: add new commits.