rm base/config/kconfig/Makefile.kconfig.orig

Apparently committed by accident, either at the time of the ShabbyX
fork or else in the upstream RTAI tree.

This gets automatically removed by `dh_clean`.  Removing it here
instead of making an exclusion for this file in the packaging.
Fix `distclean` target

Don't remove `./configure`.  GNU coding standards say the `distclean`
target should not remove anything needed to run `./configure`.

Include `doc` directory for build and clean.
base/sched/Kbuild:  initial commit:  satisfy kbuild 'make clean'

/usr/src/linux-headers-`uname -r`/scripts/Makefile.clean wants to
include either 'Kbuild' or 'Makefile' in the 'base/sched' directory.
Revert last commit:  remove base/sched/Kbuild

This didn't work, and I don't know what will, but I'd better unbreak
this.  Oops.
Fix `make distclean`:  Create `Makefile` symlinks for all arches

The `distclean` target runs the kbuild `clean` target in *each
subdirectory* in `$(DIST_SUBDIRS)`, and that requires `Makefile` to
exist.  The `Makefile` in each subdir is a symlink created by
`./configure`, which only created a symlink for the target arch and
not other arches.  This caused `distclean` to fail when running the
kbuild `make clean` in non-target arch directories.

This commit simply adds symlinks in all arch subdirectories so that
`make distclean` completes successfully.
One more `distclean` fix

- don't create Makefile in m68knommu arch directory
  - another piece of unused flotsam?
- add 'Makefile' to arm arch `DISTCLEANFILES`
Add -lpthread to liblxrt LDFLAGS

dpkg found `liblxrt.so` isn't being linked with `libpthread`:

     dpkg-shlibdeps: warning: symbol __pthread_register_cancel used by debian/librtai1/usr/lib/liblxrt.so.1.0.0 found in none of the libraries
     dpkg-shlibdeps: warning: symbol pthread_create used by debian/librtai1/usr/lib/liblxrt.so.1.0.0 found in none of the libraries
     dpkg-shlibdeps: warning: symbol pthread_testcancel used by debian/librtai1/usr/lib/liblxrt.so.1.0.0 found in none of the libraries
     dpkg-shlibdeps: warning: symbol pthread_attr_setstacksize used by debian/librtai1/usr/lib/liblxrt.so.1.0.0 found in none of the libraries
     dpkg-shlibdeps: warning: symbol __pthread_unregister_cancel used by debian/librtai1/usr/lib/liblxrt.so.1.0.0 found in none of the libraries
     dpkg-shlibdeps: warning: symbol pthread_join used by debian/librtai1/usr/lib/liblxrt.so.1.0.0 found in none of the libraries
     dpkg-shlibdeps: warning: symbol pthread_kill used by debian/librtai1/usr/lib/liblxrt.so.1.0.0 found in none of the libraries
RTAI init script is now automatically installed

Signed-off-by: Shahbaz Youssefi <ShabbyX@gmail.com>
Add rt_task_next_period to user-space

next_period was useful to get the time left until next period of the
task, but it was only in kernel space.  This commit changes that to
rt_task_next_period, and adds a NEXT_PERIOD syscall that lets that
functionality be used in user-space too.

Signed-off-by: Shahbaz Youssefi <ShabbyX@gmail.com>