shared/Lock.pm: fixed a small bug (now returns 0 if occupied)

shared/Posting/Write.pm: comments added and some things modified to work with new 'fo_posting.pl'
shared/Posting/_lib.pm: inserted 'create_new_thread' and 'create_message' from Posting::Write
user/fo_posting.pl: should now run stable
user/config/*.xml: adjusted to work with new 'fo_posting.pl'