This tests the various parts of atomic that I want to make
interruptible. Running with --debug shows the stats from
__igt_sigiter_continue, which can be used to make sure that
we don't fall over.

The default igt kms helpers use drmIoctl, which is not intercepted
by igt_while_interruptible. Only igt_ioctl is. This means we have
to call the ioctls manually here.

Changes since v1:
- Implement interruptible DPMS checking too.
- Use igt_ioctl + igt_while_interruptible, instead of the signal helper
  shotgun.
Changes since v2:
- Bump whitespace to get rid of the weird double } at same indent.
- Use more newlines in the call to the atomic ioctl.
Changes since v3:
- Fix copyright on year. (Adrinael)
- Use do_ioctl instead of do_or_die(igt_ioctl) (ickle).
- Add test description. (Adrinael)

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Daniel Stone <daniels@collabora.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> #v1
Reviewed-by: Petri Latvala <petri.latvala@intel.com>
[mlankhorst: Document sleep values (Adrinael)]