Pull changes from gentoo-x86

As discussed previously in our internal mails, I made some changes to the ebuilds.
What is missing from the comments in the commits is:

* use `FEATURES="test"` when playing with ebuilds (especially perl since many of them have tests) and see whether they run and possibly need more packages. If you need additional packages only for testing, you can use `"test? ( ... )"` and add `"test"` to `IUSE`. `FEATURES="test"` automatically sets `USE="test"`.
* use `repoman full` in an ebuild directory to check for possible QA issues (part of gentoolkit-dev; make sure that your portage tree is up-to-date before)