Adds some debian specific native compile options. Adds an option to build using libav.

git-svn-id: https://svn.java.net/svn/jitsi~svn/libjitsi@10422 198c5059-ef06-4ec0-9a75-fdd6b0ef00a6
All Metaswitch fixes to date
Fix build and add a gitignore file.