:Goal, -Id, +Options)Create a thread in Pool. Options overrule default
thread creation options associated to the pool. In addition, the
following option is defined:
true (default) and the pool is full, wait until a member
of the pool completes. If
false, throw a resource_error.
resource_error(threads_in_pool(Pool)) is raised if wait
false or the backlog limit has been reached.
existence_error(thread_pool, Pool) if Pool
does not exist.