Blender Git Loki

Mesh Batch Cache: Add support for uv/vcol/tangent data layers.

This is a bad implementation waiting for some improvement that are :
- Gawain support for multiple names. -> will remove duplication of attribute alloc
- Glsl safe name string escaping. -> will remove any risk of hash colision.

Old glsl drawing was relying on attribute being choosen by DerivedMesh at drawing time.
For this reason, we declare all possible attrib "name" for each data layer inside the batches.
In the glsl code, we declare required data by type and name.
Then Gawain only bind vbos if names correspond.
This is way cleaner as we do not need to access the CD itself when drawing.

One other problem is that the hash maybe 11 caracters long and rapidly overload gawain's attrib name buffer.