Bug 1074004 - Update nestegg from upstream.  r=giles

--HG--
rename : media/libnestegg/README => media/libnestegg/README.md
Bug 1074004 - Fix WebMioData implementation in TestWebMWriter.  r=giles
Bug 1069660 - Factor Vorbis and Opus decoding out.
Bug 1069660 - WebMReader cleanups.
Bug 1069660 - Enforce DiscardPadding validity.
Bug 1069660 - Add mochitests for WebM/Opus files with invalid DiscardPadding.
Bug 1069660 - Wrap long lines at 80 cols.