* fhandler.h (class fhandler_mailslot): Move down in file and change

	* fhandler.h (class fhandler_mailslot): Move down in file and change
	parent class to fhandler_base_overlapped.  Remove declaration of
	method write.  Add declaraiotns for raw_read and raw_write.
	* fhandler_mailslot.cc (fhandler_mailslot::fhandler_mailslot): Call
	fhandler_base_overlapped constructor.
	(fhandler_mailslot::fstat): Call fhandler_base_overlapped::fstat.
	(fhandler_mailslot::open): Drop FILE_SYNCHRONOUS_IO_NONALERT flag from
	call to NtOpenFile.
	(fhandler_mailslot::raw_read): New method.
	(fhandler_mailslot::raw_write): Ditto.  Take over length algorithm from
	former write method.
	(fhandler_mailslot::write): Remove.
	(fhandler_mailslot::ioctl): Call fhandler_base_overlapped::ioctl.