[arch-releng] [RFC][archiso] A rain of patches

Note if you want to test this without using util-linux 2.21 (not released yet), must use these boot params: earlymodules=loop loop.max_loop=16 Currently archiso_shutdown is broken due recent /lib -> /usr/lib of udev. One patch in this series fixes it, this is mostly important when using cow_device otherwise there is no harm. If there any plans to make new officials images soon (before util-linux 2.21), I like to push all these patches, plus adding temporary workaround (mentioned boot params) to syslinux.cfg.