If $dumpdev is set to AUTO, use the first suitable swap partition listed

in /etc/fstab, or print an error message if no suitable device was found.

MFC after:	4 weeks

etc/rc.d/dumpon

@@ -22,6 +22,16 @@ dumpon_start()
 	case ${dumpdev} in
 	[Nn][Oo] | '')
 		;;
+	[Aa][Uu][Tt][Oo])
+		memsize=$((`/sbin/sysctl -n hw.physmem` / 1024))
+		while read dev mp type more ; do
+			[ "${type}" = "swap" ] || continue
+			[ -c "${dev}" ] || continue
+			/sbin/dumpon -v "${dev}" 2>/dev/null && return 0
+		done </etc/fstab
+		echo "No suitable dump device was found." 1>&2
+		return 1
+		;;
 	*)
 		/sbin/dumpon -v ${dumpdev}
 		;;