Add dedicated buttons for scope switching

Previously, changing to a different scope was done by clicking the scope
type button and cycling through all scopes. This commit decreases the
number of clicks needed to switch between two scopes by adding a radio
selector. The radio buttons can be shown or hidden by pressing the scope
type button. This commit also makes the raw histogram one of the scope
types.

rtengine/improccoordinator.cc

@@ -358,6 +358,7 @@ void ImProcCoordinator::updatePreviewImage(int todo, bool panningRelatedChange)
             }
 
             imgsrc->getRAWHistogram(histRedRaw, histGreenRaw, histBlueRaw);
+            hist_raw_dirty = !hListener->updateHistogramRaw();
 
             highDetailPreprocessComputed = highDetailNeeded;
 
@@ -2471,6 +2472,19 @@ void ImProcCoordinator::requestUpdateHistogram()
     }
 }
 
+void ImProcCoordinator::requestUpdateHistogramRaw()
+{
+    if (!hListener) {
+        return;
+    }
+    // Don't need to actually update histogram because it is always
+    // up-to-date.
+    if (hist_raw_dirty) {
+        hist_raw_dirty = false;
+        notifyHistogramChanged();
+    }
+}
+
 void ImProcCoordinator::requestUpdateVectorscopeHC()
 {
     if (!hListener) {