Asset library: Share materials instead of copying them

NOTE this is not necessarily safe! It's just intended as an illustration.

Load time: 1.88s -> 1.46s
Render scene med. time: 2.56ms -> 1.95ms

SoftwareOcclusionCulling/CPUT/CPUT/CPUTAssetLibrary.cpp

@@ -339,10 +339,16 @@ CPUTMaterial *CPUTAssetLibrary::GetMaterial(const cString &name, bool nameIsFull
         // Not looking for an instance, so return what we found
         return pMaterial;
     }
+#if 1
+	if ( !created )
+		pMaterial->AddRef();
+	return pMaterial;
+#else
     CPUTMaterial *pClone = pMaterial->CloneMaterial( absolutePathAndFilename, pModel, meshIndex);
 	if ( created )
 		pMaterial->Release(); // We don't want to hold a reference to the master.
     return pClone;
+#endif
 }