[sys-kernel/*] spring cleanup, drop anything <3.0
[sys-kernel/*] bump 3.8 kernels to 3.8.3
[sys-fs/udev] revision bump, sync with Portage
[sys-fs/udev-init-scripts] no longer needed, since udev in Portage supports kernel 2.6.32
[eclass] sabayon-kernel: add K_TARBALL_EXT support, migrate from bz2 to xz

See Gentoo #421721
[sys-kernel/*] re-Manifest after the xz migration
[sys-kernel/*] last round of cleanup after the xz migration
[sys-kernel/genkernel] add a patch for making Linux 3.8 ehci-hcd work as expected