Fix class/struct warnings.

src/AdornedRulerPanel.h

@@ -17,7 +17,7 @@
 #include "ViewInfo.h" // for PlayRegion
 
 class AudacityProject;
-class SelectedRegionEvent;
+struct SelectedRegionEvent;
 class SnapManager;
 class TrackList;
 

src/EnvelopeEditor.h

@@ -14,7 +14,7 @@
 class wxMouseEvent;
 class wxRect;
 class Envelope;
-class TrackPanelDrawingContext;
+struct TrackPanelDrawingContext;
 class ZoomInfo;
 
 // A class that holds state for the duration of dragging

src/Menus.cpp

@@ -644,7 +644,6 @@ bool MenuManager::TryToMakeActionAllowed(
    CommandFlag & flags, CommandFlag flagsRqd )
 {
    auto &project = mProject;
-   bool bAllowed;
 
    if( flags.none() )
       flags = GetUpdateFlags();

src/TrackPanelDrawable.h

@@ -12,10 +12,10 @@ Paul Licameli
 #define __AUDACITY_TRACK_PANEL_DRAWABLE__
 
 struct TrackPanelDrawingContext;
-struct wxRect;
+class wxRect;
 
 /// \brief Drawing interface common to cells, groups of cells, and temporary handles in CellularPanel
-class TrackPanelDrawable {
+class AUDACITY_DLL_API TrackPanelDrawable {
 public:
    virtual ~TrackPanelDrawable() = 0;
 

src/tracks/labeltrack/ui/LabelGlyphHandle.h

@@ -15,7 +15,7 @@ Paul Licameli split from TrackPanel.cpp
 
 class wxMouseState;
 class LabelTrack;
-class LabelTrackEvent;
+struct LabelTrackEvent;
 class NotifyingSelectedRegion;
 class ZoomInfo;