Working version of mesh decimation code which acts directly on vertex/index buffers.

Also initial work on a 'dynamic' mesh for simplification... but this probably won't be needed now.

library/PolyVoxCore/include/PolyVoxForwardDeclarations.h

@@ -39,6 +39,13 @@ namespace PolyVox
 	typedef Volume<uint16_t> UInt16Volume;
 	//---------------------------------
 
+	//---------- Mesh ----------
+	class Mesh;
+	class MeshEdge;
+	class MeshFace;
+	class MeshVertex;
+	//---------------------------------
+
 	class IndexedSurfacePatch;
 	class Region;
 	class SurfaceVertex;