python: remove 2.6 as a supported version

2.6 is no longer an allowed value by the upstream python eclass.
profiles: disable dependency on x11-misc/shared-mime-info

Newer versions of glib pull in this package simply because lots of
glib/gtk apps need it. This isn't applicable to us.
profiles: break dependency loop between glib and pkg-config
vim: fix cross-compiling, newer ebuilds rely on broken auto-detection
portage: fix stage1 builds involving new slot dependencies

Really screwy crud going on here, see the upstream bug for details:
https://bugs.gentoo.org/show_bug.cgi?id=520112
update_engine: remove coredumping code, fix glib compatibility
chore(metadata): Regenerate cache
Merge pull request #797 from marineam/updates

Updates for compatibility w/ upstream portage tree