RDP compositor take 6

This patch is the 6th version of the FreeRDP based compositor.
Changes from last version:
 * use pixman_image_get_stride() when appropriate
 * always realloc

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
compositor: add information about the fbdev backend to --help output
window: don't execute the selected menu item when getting popup_done
compositor: Use wl_pointer_set_current to cleanup after surface destruction

This API call handles setting the current surface on the wl_pointer and also
maintaining a destroy notification to monitor that surface for destruction.

This is part of the fix for: https://bugzilla.gnome.org/show_bug.cgi?id=696946
autotools: Add a libunwind configure switch

Signed-off-by: Quentin Glidic <sardemff7+git@sardemff7.net>
Fix compiler warnings

This prevents compiler warnings when using libpng 1.6 and GCC 4.8
compositor-drm: Allow running without launcher if effective UID is 0

This lets us keep running weston as root or setuid root.
Make backends always specify output repaint time

Most backends relies on gettimeofday(2) for output repaint timestamps
but this is not a requirement. Before this patch repaints coming from
idle_repaint() always used gettimeofday(2) for timestamps. For backends
not using that time source this could cause large jumps between
timestamps.

To fix this, timestamps needs to always come from the backend. This
means that the backend needs to always be responsible of starting the
repaint loop in case that the repaint cannot start immediately.

The drm backend implementation is from the patch by Ander Conselvan de
Oliveira found here:
http://lists.freedesktop.org/archives/wayland-devel/2013-February/007393.html

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>