Add detection of Opus to Matroska IDs in codectype.cpp
Fix alignment of the Matroska IDs after adding A_OPUS/EXPERIMENTAL
Add H265/HEVC to the Matroska IDs in codectype.cpp

The V_MPEGH/ISO/HEVC designation is part of the draft for HEVC's
inclusion in Matroska.
Merge pull request #124 from qyot27/new_codectypes

Add Opus and (tentative) HEVC to codectypes
Fix compilation with things other than ffmpeg master. Closes #126.