Fix debian package builds for xenomai and rtai

- Build Xenomai if libxenomai-dev pkg is installed
  - linux-image-*xeno* is not a build dep
- Remove linux-image-xenomai version dependency in linuxcnc-xenomai pkg
  - xeno-user threads are kversion independent
- Fix linuxcnc-rtai-kernel package file globs
- Fix things needing to be called 'rtai-kernel' to be picked up properly

Fixes #155
Merge pull request #164 from zultron/mk-pull

Fix debian package builds for xenomai and rtai
motion: add motion.current-motion pin.

This reflects the current motion type:

#define EMC_MOTION_TYPE_TRAVERSE 1
#define EMC_MOTION_TYPE_FEED 2
#define EMC_MOTION_TYPE_ARC 3
#define EMC_MOTION_TYPE_TOOLCHANGE 4
#define EMC_MOTION_TYPE_PROBING 5
#define EMC_MOTION_TYPE_INDEXROTARY 6

In a paused state or when not currently executing a motion, the pin is
set to zero.