skins2: remove some leftovers

interaction_Register and interaction_Unregister are weird #define
 that don't seem used at all nowadays

modules/gui/skins2/src/vlcproc.cpp

@@ -190,8 +190,6 @@ VlcProc::VlcProc( intf_thread_t *pIntf ): SkinObject( pIntf ),
 
     // initialize variables refering to liblvc and playlist objects
     init_variables();
-
-    interaction_Register( pIntf );
 }
 
 
@@ -211,8 +209,6 @@ VlcProc::~VlcProc()
         m_pVout = NULL;
     }
 
-    interaction_Unregister( getIntf() );
-
     var_DelCallback( getIntf()->p_sys->p_playlist, "volume",
                      onGenericCallback, this );
     var_DelCallback( getIntf()->p_libvlc, "intf-toggle-fscontrol",