Set UID_MIN to 1001 to make sure that useradd does not automatically add users with UID 1000.

This guarantees that UID 1000 is available when post-common adds the main user at the end of the first run of crouton.

Protect GID 1000 in the same way.

Fixes a bug when xbmc is selected during the Arch install (the xmbc user created by the package steals UID 1000).
Arch installer.
Arch: source /etc/profile in enter-chroot.
Arch: Core and post-common targets.
Arch: x11/xephyr targets
Arch: Most DE and X11-related targets.
Arch: Chrome target.
Arch: KDE target (Not fully working on Arch: no launcher to start other applications?)
Arch: gnome target (not working).
Arch includes Gnome 2.8, which does not have an automatic fallback
Even using gnome-flashback-session does not seem to help: startgnome
on xephyr complains about lack of hardware AND software acceleration.
Finally, /etc/X11/xinit/xinitrc behaviour is very different in Ubuntu vs
Arch (it is a fallback xinitrc in Arch, but Ubuntu's sources /etc/X11/Xsession)
Arch: Add cinnamon target. Not working on Arch (similar reasons as gnome).
Arch: Add desktop file for extension

Allows it to be set as default browser.
Arch: Fix audio.
Arch: 30-audio test.
Arch: Silence out 'Ignoring unknown extended header keyword' during bootstrap extraction.