adapt to current libav

Signed-off-by: Marcin Juszkiewicz <marcin@juszkiewicz.com.pl>
reijo.pro: link with avutil for av_freep@@LIBAVUTIL_51 symbol

Signed-off-by: Marcin Juszkiewicz <marcin@juszkiewicz.com.pl>
Fix complilation with modern libavcodec
Make things compile with clang
Updating .gitignore