Fix copyright throughout.

	Fix copyright throughout.
	Eliminate use of _impure_ptr outside Cygwin.
	* bsd_helper.cc: Include errno.h instead of cygerrno.h.
	* bsd_mutex.cc : Ditto.
	* client.cc: Ditto.
	* cygserver.cc: Ditto.
	* process.cc: Don't build functions inside Cygwin.  Don't include
	cygerrno.h.  Don't set errno.
	* transport_pipes.cc (SET_ERRNO): New define.  Use througout.
	* transport_sockets.cc (SET_ERRNO): Ditto.
	(GET_ERRNO): Ditto.