Removed "lock channels" CheckButton, it wasn't very useful. Keeping the "(lead)" note on the green channel label, to give a hint that this slider controls the other two as well.

rtgui/filmnegative.h

@@ -71,7 +71,6 @@ public:
 
 private:
     void editToggled();
-    void lockChannelsToggled();
 
     const rtengine::ProcEvent evFilmNegativeExponents;
     const rtengine::ProcEvent evFilmNegativeEnabled;
@@ -84,9 +83,6 @@ private:
     Adjuster* const greenExp;
     Adjuster* const blueExp;
 
-    Gtk::CheckButton* const lockChannels;
-    sigc::connection lockChannelsConn;
-
     Gtk::Grid* const spotgrid;
     Gtk::ToggleButton* const spotbutton;
     sigc::connection spotConn;