Set the TTY mode appropriately at startup, and clean it up
when the compositor exits. Also, take control of VT switching,
including the calls to drmSetMaster and drmDropMaster as appropriate.
In the future, we the kernel implements the mute evdev ioctl,
we'll also make sure that input devices are appropriately released.
https://bugzilla.gnome.org/show_bug.cgi?id=705861
To run mutter as a display server, one needs to acquire and
release the DRM master, which is only possible for root, so
we take advantage of weston-launch, a small setuid helper binary
written for the weston project. We import our own slightly
modified copy of it, because weston-launch only launches weston,
for security reasons.
https://bugzilla.gnome.org/show_bug.cgi?id=705861
