audio/aqualung: Fix build with FFmpeg 3.0.x

[woodsb02]

Summary

audio/aqualung: Fix build with FFmpeg 3.0.x

Add patch-ffmpeg3, obtained from upstream [1], to allow aqualung to
build successfully once multimedia/ffmpeg is updated to 3.0.x.
Note that multimedia/ffmpeg is currently still on the 2.8.x branch,
however this patch is backwards compatible with ffmpeg 2.8.x.

[1] https://github.com/jeremyevans/aqualung/commit/3f60efe3dbab8e9d2c07a7b183fd009b3c999d60

Test Plan

poudriere testport audio/aqualung

[woodsb02]

Thanks for the review mat. Waiting on maintainer feedback from Chris Hutchinson before committing.

[portmaster_BSDforge.com]

In D6820#143262, @woodsb02 wrote:

Thanks for the review mat. Waiting on maintainer feedback from Chris Hutchinson before committing.

Thanks for all the time, and work you put into this.

Looks good!

--Chris