Remove all trailing spaces

No real changes, just clean up sources by removing trailing spaces from
all the non-generated files.

This should hopefully avoid future commits mixing significant changes
with insignificant whitespace ones.

interface/wx/sashwin.h

@@ -275,7 +275,7 @@ public:
     */
     wxSashEdgePosition GetEdge() const;
 
-    
+
     void SetEdge(wxSashEdgePosition edge);
     void SetDragRect(const wxRect& rect);
     void SetDragStatus(wxSashDragStatus status);