* cygthread.cc (cygthread::async_create): Define new function.

* cygthread.cc (cygthread::async_create): Define new function.
* cygthread.h (cygthread::create): Use correct regparm.
(cygthread::standalone): Delete from class and from all constructors.
(cygthread::cygthread): Use three only arguments for detached threads, and
start the thread via QueueUserAPC/async_create.
* dcrt0.cc (dll_crt0_0): Remove handling for wincap.has_buggy_thread_startup.
(dll_crt0_1): Ditto.
* wincap.cc: Ditto throughout.
* wincap.h: Ditto.