* dcrt0.cc (child_info_fork::alloc_stack_hard_way): Check if the

	* dcrt0.cc (child_info_fork::alloc_stack_hard_way): Check if the
	requested stack is application-provided within the user heap or an
	mmapped region.  If so, just use it.  Add comment to explain why.
	* miscfuncs.cc (thread_wrapper): If an application-provided stack
	has been given, implement cygtls area at the stackbase.  Fix comment.
	* mmap.cc (is_mmapped_region): New function.
	* winsup.h (is_mmapped_region): Declare.