* cygerrno.h (__seterrno_from_nt_status): Define. Always set Win32

	* cygerrno.h (__seterrno_from_nt_status): Define. Always set Win32
	error code as well as errno. Use throughout where errno is set from
	NT status.
	(set_errno): Evaluate val only once.
	* fhandler_disk_file.cc (fhandler_base::fstat_by_handle): Fix typo in
	debug output.
	* fhandler_mem.cc (fhandler_dev_mem::open): Rely on
	__seterrno_from_nt_status setting Win32 error code in debug output.
	* fhandler_proc.cc (format_proc_uptime): Ditto.
	(format_proc_stat): Ditto.
	* fhandler_process.cc (format_process_stat): Ditto.
	* sysconf.cc (sysconf): Ditto.