eudev: does not work without /run
rc.boot: use udev instead of mdev if available
eudev: prevent renaming of ethernet interfaces
linux.config: do not use framebuffer drivers

according to https://wiki.gentoo.org/wiki/Xorg/Configuration
the KMS and FB drivers conflict, and this seems indeed to be the case.
maybe the FB_VESA driver should be disabled as well.
linux.config: add some settings which made X work

actually the previous commit could be responsible for a working X,
since i applied both changes at once.