* Make test-app_server work again in a launch_daemon environment
* test_registrar gets a separate signature and port name again so the
host system can distinguish it from the system registrar
* AppServer is normally a BServer now, however, there can't be two
BApplications in one team. A class TestServerLoopAdapter is added,
which becomes the base class of AppServer instead of BServer when
compiling for libbe_test. It's an adapter class which looks towards
AppServer as it if was a BServer, but internally it is derived from
MessageLooper (like the old AppServer before the transition to
BServer).
This way, AppServer can stay a BServer in normal builds and it also
avoids having to use too many #ifdefs to distinguish the two
versions.