Theora texture for cloned material fix

When a TSShapeInstance makes a copy of its own materials through
cloneMaterialList() (such as done with client side ShapeBase objects),
the reference to a named diffuse render target was being lost.  This
affected using a TheoraTextureObject on a ShapeBase derived object
(StaticShape, etc.).
Merge pull request #382 from DavidWyand-GG/TheoraTexMatClone

Theora texture for cloned material fix