Revert "removed specific case for vertex attributes starting with DiffuseTexCoord (also fixes bug when no such attributes are present and semantics start at TEXCOORD1)"

This reverts commit 676312593eda7c372ecb421a492a3e3080bdca69.
Replaced DiffuseTexCoord by TextureCoodinate in FunctionInliner:UpdateStructureTexCoordSemantics