threaded/1 calls fail to cleanup all created threads on thread creation resource error

[pmoura]

A threaded/1 call may fail to cleanup all created threads on thread creation resource error. A common resource error is the exhaustion of virtual memory address space when using 32 bits versions of a back-end Prolog compiler such as SWI-Prolog. This problem may result in orphaned threads, some of them continuing running subgoals instead of being aborted as a consequence of the resource error.