Fixed pHash-0.9.6 compatibility with Latest ffmpeg 2.3

See my patch for pHash-0.9.6 on https://github.com/hszcg/pHash-0.9.6/commit/85218a6443f93d0bbafc4d36c8c6ab9673d0d2c5

This patch resolved the issue about **Segmentation Fault error when trying to compare two videos with pHash library and its ruby bindings** , see http://stackoverflow.com/questions/23414036/segmentation-fault-error-when-trying-to-compare-two-videos-with-phash-library-an