common shm library: link with -lrt for shm_open(), shm_unlink()
hal_lib: link with common shm API library too
configure.in: rtai_shm.ko doesnt exist (at least in 2.6.32-122-rtai)
rtapi/rtai: delete RTAI-specific shm code

superseded by common shm API to shmdrv
rtapi_msgd: mlock() the global segment

theory: a thread doing rtapi_print*() might fault
not sure if this helps, but doesnt damage either
linuxcnc.in:  remove obsolete test for KERNEL_VERS

Breaks linuxcnc.  This whole script needs to be revisited.
Makefile:  don't warn about frame sizes for user threads

https://github.com/zultron/linuxcnc/issues/13
rtapi_compat.c:  hardcode kmodule extension and print diagnostics on failure

flavor_t mod_ext is '.so' for userland threads; now hardcoded to
'.ko'.
realtime.in:  fix shmdrv unloading behavior

Don't unload shmdrv if shm segments still exist.  This allows multiple
instances.

Also, during load, bomb out if shmdrv.ko was inserted but doesn't come
online.
.gitignore several bits of build cruft
Makefile.inc.in:  set default thread style to first in detected list

Can't build posix threads when posix threads are disabled!