prepare for 7.4.7 release
regression fix: read queue spool directory after config file has been processed

note that this does not yet support legacy style $WorkDir
re-enable legacy $WorkDir for queue spool directory use
bugfix: prevent a segfault during imtcp's shutdown

If imtcp is loaded and no listeners are configured (which is uncommon),
rsyslog crashes during shutdown.

The cause is that startWorkerPool() is called unconditionally during
modExit() even if there are no listerners. Correcting this triggers a
memleak of the wrkrMut mutex which shouldn't have been destroyed in
startWorkerPool() in the first place.
doc: maintain ChangeLog
bugfix: prevent a memleak in imtcp

This cleans up a memleak triggered by the previous commit