WARN: postinst
You must rebuild all drivers if upgrading from <xorg-server-1.12
because the ABI changed. If you cannot start X because
of module version mismatch errors, this is your problem.
You can generate a list of all installed packages in the x11-drivers
category using this command:
	emerge portage-utils; qlist -I -C x11-drivers/
or using sets from portage-2.2:
	emerge @x11-module-rebuild