Fix compilation on Linux:

- The template addition is apparently a C++ Standard thing which is a bit of a mess but the way GCC interprets it requires these.
 - In XOrg there is a struct called 'Region' which causes ambiguities. For some reason doing 'using PolyVox::Region' didn't fix it.

library/PolyVoxCore/include/MeshDecimator.inl

@@ -112,6 +112,7 @@ namespace PolyVox
 		}
 	}
 
+	template<>
 	void MeshDecimator<PositionMaterial>::fillInitialVertexMetadata(std::vector<InitialVertexMetadata>& vecVertexMetadata)
 	{
 		vecVertexMetadata.clear();
@@ -171,6 +172,7 @@ namespace PolyVox
 		}
 	}
 
+	template<>
 	void MeshDecimator<PositionMaterialNormal>::fillInitialVertexMetadata(std::vector<InitialVertexMetadata>& vecVertexMetadata)
 	{
 		vecVertexMetadata.clear();