manifest: Track own external/libvorbis

Google has not published most recent 8.1.0_r30 tag for external/libvorbis
and instead declared the patch for CVE-2018-5146 "non-public".
Hence we need to track our own fork of it.

Change-Id: I3b9e27daf58ede43cff225faff43258d36c78a8e
1 file changed
tree: 90c02890e6dd5f0bbc63c31a92a258d3df0ef608
  1. snippets/
  2. default.xml
  3. README.mkdn