Fix of

"Multimaterial printer switches filament at the wrong time during a print"
https://github.com/prusa3d/Slic3r/issues/607

There was a single layer between the raft top and the object first layer
missing on the wipe tower, and after this missing layer all the tool
changes were shifted by one layer, meaning two color print had the colors
switched.

xs/xsp/Print.xsp

@@ -91,7 +91,6 @@ _constant()
     size_t support_layer_count();
     void clear_support_layers();
     Ref<SupportLayer> get_support_layer(int idx);
-    Ref<SupportLayer> add_support_layer(int id, coordf_t height, coordf_t print_z);
 
     bool step_done(PrintObjectStep step)
         %code%{ RETVAL = THIS->state.is_done(step); %};