Add some plumbing in our top level Makefile to make life easier

Add some plumbing in our top level Makefile to make life easier

For instance you can type make bin/smbd to build just smbd (and it's
dependencies still) or make bin/smbd bin/smbtorture

You can also do make service_drepl if you want just to build the stuff
related to DRS

Change-Id: I61bdaeff79ecfb1a15728c2de7e6a6a14dd8bc7d
Signed-off-by: Matthieu Patou <mat@matws.net>
Reviewed-by: Michael Adam <obnox@samba.org>
Autobuild-User(master): Matthieu Patou <mat@samba.org>
Autobuild-Date(master): Fri Sep 26 11:48:11 CEST 2014 on sn-devel-104