[8u, 9] Review request for 8136920: Provide media support for libav version 55 and 56

[Alexander Matveev]

Hi Kevin and Kirill,

Please review the following:
https://bugs.openjdk.java.net/browse/JDK-8136920
http://cr.openjdk.java.net/~almatvee/8136920/webrev.9.00/
8u backport: http://cr.openjdk.java.net/~almatvee/8136920/webrev.8u.00/

Added support for libavcodec55, libavcodec56 and libavcodec-ffmpeg56.

Thanks,
Alexander