deb: new debian/configure and debian/control

This one's written in python instead of bash, and has a cleaner internal
structure.

This handles the flavored debs of the unified-build-candidate branch.

The new debian packaging produces linuxcnc.deb, linuxcnc-dev.deb,
and linuxcnc-doc-*.deb, just like before, and in addition produces
linuxcnc-$FLAVOR.deb for each flavor enabled by debian/configure.
The available flavors are:

    posix (what we used to call sim)

    rtai-kernel (what we used to call rt)

    rt-preempt

    xenomai

    xenomai-kernel

linuxcnc.deb depends on at least one of the flavor debs, and suggests
all of them (to make them easy to find in the package manager, mostly).
deb: fix the debian/{control/rules} remaking rules

The code in debian/rules.in for rebuilding debian/control has been broken
for a good long while.  This commit fixes that, and unifies it with the
rule for rebuilding debian/rules.  Also changes the name of the subst
variable to be more descriptive.
deb/conf: accept -a to mean -r

"debian/configure -r" is supposed to mean "configure for the running
realtime kernel", and "debian/configure -a" is supposed to mean "configure
for any realtime headers you can find on the system".

The buildbot ill-advisedly runs 'debian/configure -a', even though it
knows it's going to run runtests later (so the kernel it builds for must
be the one that's running).  So really -r would be more correct.

In practice it's fine because all the buildslave VMs only have one
realtime kernel installed, so there's no difference between -a and -r
on those hosts.

If someone cares strongly about the difference between the old "-a"
and the new "-a" we can reinstate it.

As an aside, it probably makes sense to add a "debian/configure --all"
option that examines the apt database and makes the dsc build-depend on
all *available* realtime kernel headers.
deb/control: get rid of ancient Provides in control

I think it's time to stop worrying about users upgrading from emc2.deb
packages.
deb/control: relax the Conflicts

The flavor packages should conflict with pre-ubc packages, but there's
no convenient way to specify that currently.

When we merge ubc into master we'll tag that point as 2.6.0-pre1,
and make the post-ubc debs conflict with linuxcnc < 2.6.0-pre1.
deb/rules: dont use cpio when cp will do

Debian Wheezy doesn't come with cpio by default, this commit lets us
not add a build-dependency on it.
install rsyslogd.conf file
give dlopen the path to the ulapi library

Normally dlopen() searches LD_LIBRARY_PATH and /lib and /usr/lib.  In rip
builds we set LD_LIBRARY_PATH and we could do the same in installed
scripts, but it seems simpler to teach ulapi where the files live.
put ulapi-$flavor.so straight into rtlib/, not lib, so the dlopen can look in EMC2_RTLIB_DIR