sbcl no longer supports (sb-thread:current-thread-id). bryan d. o'connor bryan@lunch.org**20050830023327]

openmcl-threads using semaphores. bryan d. o'connor bryan@lunch.org**20050901181244]

allegro-threads using gates. bryan d. o'connor bryan@lunch.org**20050901235948 patch written by Dirk Gerrits.