Original commit message from CVS:
* configure.ac:
Check for X11
* sys/v4l2/gstv4l2object.c: (gst_v4l2_class_probe_devices):
* sys/v4l2/gstv4l2object.h:
* sys/v4l2/gstv4l2src.c: (gst_v4l2src_iface_supported):
* sys/v4l2/gstv4l2src.h:
* sys/v4l2/gstv4l2xoverlay.c: (gst_v4l2_xoverlay_open):
* sys/v4l2/gstv4l2xoverlay.h:
Code cleanups, fix debug macros