m_ids in Points scehma should be a 64-bit type

Currently, a 32-bit identifier (signed int) is used for particle ID in the 
AbcGeom Points schema.  This breaks quickly, as there's only 4.3 billion of 
them to go around. That sounds like a lot, but as particle ids are usually 
unique to a particle across a simulation, rather than at a single sample, if 
you have a sim with a few million particles that are being born and dying at a 
rapid rate, in a few hundred frames you exhaust this pretty quickly.

Because this is a binary-data-compatibility issue, it is in 0.9

Original issue reported on code.google.com by ard...@gmail.com on 16 Nov 2010 at 11:03

PiRSquared17 / alembic

m_ids in Points scehma should be a 64-bit type #88