Weekly pre-release

New features:

• Enabled assembly for Windows x86_64 builds.
• Speed-ups in Motion Estimation, with new x86/x86_64 simd optimizations.
• Diamond Search in motion estimation.
• RDO Speedups

Bugfixes:

• Fix the memory allocation alignment issues found on windows x86_64.
• Fix container_sequence_header()
• Additional fixes to the 422 codepaths.
• More smaller and larger bugfixes

API Changes:

• Large simplification: now it is possible to encode by using onlysend_frame() and receive_packet().
• Update and document EncoderStatus variants.

Internal changes:

• Lots of refactoring to prepare for new features (tile support, tile and segment threading)
• Improvements to debug builds and tests to accelerate development
• Additional tests