Gerber file generation: remove a optional info in .FileFunction: the layer type.

TF.FileFunction,Copper,L1,Top,Signal is now TF.FileFunction,Copper,L1,Top

This param is not useful, and probably never correctly set by users, because is is not used by Pcbnew.
(It is used only for dsn export)

pcbnew/pcbplot.cpp

@@ -170,6 +170,12 @@ const wxString GetGerberFileFunctionAttribute( const BOARD *aBoard, LAYER_NUM aL
         break;
     }
 
+    // This code adds a optional parameter: the type of copper layers.
+    // Because it is not used by Pcbnew (it can be used only by external autorouters)
+    // user do not really set this parameter.
+    // Therefore do not add it.
+    // However, this code is left here, for perhaps a future usage.
+#if 0
     // Add the signal type of the layer, if relevant
     if( IsCopperLayer( aLayer ) )
     {
@@ -190,6 +196,7 @@ const wxString GetGerberFileFunctionAttribute( const BOARD *aBoard, LAYER_NUM aL
             break;   // do nothing (but avoid a warning for unhandled LAYER_T values from GCC)
         }
     }
+#endif
 
     wxString fileFct;
     fileFct.Printf( "%%TF.FileFunction,%s*%%", GetChars( attrib ) );