Opus 1.1-alpha release

This is an alpha release for the upcoming 1.1 release. Compared to 1.0.2, it
includes quality improvements, optimizations, bug fixes, as well as an
experimental speech/music detector for mode decisions. All the fixes and
improvements from 1.0.2 are also in this release. The most important changes
are:

Quality-impacting

    Unconstrained VBR algorithm
    New transient detector
    Bitrate boost for tonal samples, which are harder to code
    Fixes to the tf analysis code
    Improvements to the hybrid mode code
    Fixed some mode switching issues
    More aggressive use of dynamic allocation
    Automatic audio bandwidth detection
    DC rejection filter

Optimizations

    Significant reduction of the decoder stack size requirement
    Optimization of several functions for the common case of zero
This tag has no release notes.