debian: add build-depends and section for mod_mp4

This needs a package from debian-multimedia.org, so it needs to go in
contrib/ and we can't build it as part of this source package.

debian/control-modules

@@ -139,6 +139,8 @@ Build-Depends: scons, libboost-dev, libboost-system-dev,
 Module: applications/mod_mp4
 Description: MP4 video support
  This module adds support for MP4 video playback.
+Build-Depends: libmp4v2-dev
+Section: contrib/comm
 
 Module: applications/mod_nibblebill
 Description: Nibblebill