HDF5 Alembic files are not officially supported by Blender. With this
commit, the HDF5 format is detected even when Blender is compiled without
HDF5 support, and the user is given an explanatory error message (rather
than the generic "Could not open Alembic archive for reading".
any object
There were a couple of crashes caused by stupid typos in
rB631af9f930d2fd2c76751204ff22239aa95f761d and
rB78ea06fea4a74181c25254ed72d50d8a743b6954, as well as a shamefull lack
of 'testing before committing' which only affect exporting.
One crash was due to using RNA_boolean_get instead of RNA_enum_get, the
other one was a tricky case of order of deletion happening in the
destructors of AbcExporter and ArchiveWriter.
Should not affect RC or release.