Fix problems due APT and structural changes.

- apt-pkg/acquire-item.cc: pass the expected md5 and compressed
  extenssion as empty in pkgAcqIndexTrans::pkgAcqIndexTrans(...)
  constructor;
- apt-pkg/deb/debindexfile.cc: identify translation files as trusted;
- apt-pkg/deb/debmetaindex.cc: change the way it's queue the
  translation file due a change in APT structure did in 0.6 branch;