add sysupgrade script for config preserving system upgrades. only implemented for x86-2.6 at the moment, but can be ported to other platforms easily

SVN-Revision: 8456

package/base-files/files/etc/preinit

@@ -60,6 +60,14 @@ echo "$HOTPLUG" > /proc/sys/kernel/hotplug
 eval ${FAILSAFE:+failsafe}
 lock -w /tmp/.failsafe
 mount_root
+[ -f /sysupgrade.tgz ] && {
+	echo "- config restore -"
+	cd /
+	mv sysupgrade.tgz /tmp
+	tar xzf /tmp/sysupgrade.tgz
+	rm -f /tmp/sysupgrade.tgz
+	sync
+}
 
 echo "- init -"