Blender Git Loki

Alembic: Upgrade from 1.7.8 to 1.7.12

Alembic 1.7.12 introduces a 'DCC FPS' hint, allowing Blender to write
the scene frame rate to the Alembic file. This will make it possible for
importers and converters to properly deal with situations where 'frame
number' is the only reference to time.

Writing this new DCC FPS hint will be done in a separate commit. Here
only the Alembic library is upgraded from 1.7.8 to 1.7.12.