* Makefile.in (DLL_OFILES): Add cygthread.o.

* Makefile.in (DLL_OFILES): Add cygthread.o.
* dcrt0.cc (dll_crt0_1): Eliminate various thread initialization functions in
favor of new cygthread class.
* debug.cc: Remove thread manipulation functions.
* debug.h: Ditto.
* external.cc (cygwin_internal): Use cygthread method for determining thread
name.  Remove capability for setting thread name.
* fhandler_console.cc (fhandler_console::read): Use cygthread method rather
than iscygthread function.
* fhandler_tty.cc (fhandler_tty_master::fhandler_tty_master): Use cygthread
methods to create threads.
(fhandler_tty_common::__acquire_output_mutex): Use cygthread method to retrieve
thread name.
* select.cc (pipeinf): Use cygthread pointer rather than handle.
(start_thread_pipe): Ditto.
(pipe_cleanup): Ditto.
(serialinf): Ditto.
(start_thread_serial): Ditto.
(serial_cleanup): Ditto.
(socketinf): Ditto.
(start_thread_socket): Ditto.
(socket_cleanup): Ditto.
* sigproc.cc (hwait_sig): Ditto.
(hwait_subproc): Ditto.
(proc_terminate): Ditto.
(sigproc_terminate): Ditto.
(sigproc_init): Initialize cygthread hwait_sig pointer.
(subproc_init): Initialize cygthread hwait_subproc pointer.
(wait_sig): Rely on cygthread HANDLE operator.
* strace.cc (strace::vsprntf): Use cygthread::name rather than threadname.
* window.cc (gethwnd): Use cygthread method to initialize thread.