Revert "Creating fileName.mtl file instead of fileName.obj.mtl"

This reverts commit 5757980ea5.

code/ObjExporter.cpp

@@ -124,11 +124,6 @@ std::string ObjExporter :: GetMaterialLibName()
 // ------------------------------------------------------------------------------------------------
 std::string ObjExporter :: GetMaterialLibFileName()
 {
-    // Remove existing .obj file extention so that the final material file name will be fileName.mtl and not fileName.obj.mtl
-    size_t lastdot = filename.find_last_of(".");
-    if (lastdot != std::string::npos)
-        filename = filename.substr(0, lastdot);
-        
     return filename + MaterialExt;
 }