Blender Git Loki

Modifiers: ported Surface Deform to Mesh

The modifier performed the 'bind' operation not in the bind operator,
but delayed in the mesh evaluation. This saved the result in a CoW copy
instead of in the actual modifier data. The binding operator now follows
the same approach as Mesh Deform: it forces the modifiers to run on the
real (non-CoW) data, making it possible for the modifier to store the
binding data.

This commit also ports the usage of DerivedMesh to Mesh.