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/ribbon/gallery.h

@@ -238,7 +238,7 @@ public:
             direction, @false if it did not scroll.
     */
     virtual bool ScrollLines(int lines);
-    
+
     /**
         Scroll the gallery contents by some fine-grained amount.