Comment out all derived mesh evaluation

Seems all the usecases of derived mesh are if-defed already,
so no need to have API for it in place, and definitely no
need to waste CPU ticks on converting evaluated mesh to
derived mesh.

source/blender/blenkernel/BKE_mesh_runtime.h

@@ -47,7 +47,7 @@ struct Object;
 struct Scene;
 
 /* Undefine to hide DerivedMesh-based function declarations */
-#define USE_DERIVEDMESH
+#undef USE_DERIVEDMESH
 
 #ifdef USE_DERIVEDMESH
 struct DerivedMesh;