use new source format, quilt

debian/control

@@ -2,7 +2,7 @@ Source: sdlbomber
 Section: games
 Priority: extra
 Maintainer: Stefan Bühler <stbuehler@web.de>
-Build-Depends: debhelper (>= 7), libsdl1.2-dev, libavahi-client-dev
+Build-Depends: debhelper (>= 7), libsdl1.2-dev, libavahi-client-dev, quilt
 Standards-Version: 3.9.4
 
 Package: sdlbomber

debian/source/format

@@ -0,0 +1 @@
+3.0 (quilt)