Blender Git Loki

Depsgraph: Begin concept of active dependency graph

When active dependency graph is evaluated, it will apply animation,
drivers and scalar evaluation data (such as object matrix) to an
original datablock. This way operators and tools can easily read
data from original datablock.

This will simplify porting them to copy-on-write, and solve issues
when some operator will allocate new datablock based on original one,
and will want to read data from it.