* cygthread.cc (hthreads): Remove unneeded global.

* cygthread.cc (hthreads): Remove unneeded global.
(cygthread::simplestub): New static member function.
(cygthread::runner): Don't set hthreads.
(cygthread::freerange): New member function.
(cygthread::operator new): Call freerange if all cygwin slots are used up.
(cygthread::exit_thread): Don't mess with event if freerange thread.
(cygthread::detach): Ditto.
* cygthread.h (class cygthread): Declare new member functions and variables.