[gupnp-av] (11 commits) ...Don't error out if vapigen is not found

[Jens Georg <jensgeorg src gnome org>]

Summary of changes:

  94fbec7... Add XSDData structure for document validation. (*)
  87deebf... Add some XML utility functions. (*)
  94f7fb1... Add missing G_[BEGIN|END]_DECLS. (*)
  3556793... Add DIDL-Lite related schema files. (*)
  edf5124... Add a header with GUPnP-AV enums. (*)
  545abba... Add fragment utils. (*)
  3adcf83... Add global XSDData holding DIDL-Lite schema. (*)
  01cef0d... Add gupnp_didl_lite_object_apply_fragments. (*)
  68a0fa0... Add a test checking fragment applying. (*)
  0d717f6... Add a comment explaining a bit a process of applying fragme (*)
  f162329... Don't error out if vapigen is not found

(*) This commit already existed in another branch; no separate mail sent