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/dcgraph.h

@@ -60,7 +60,7 @@ public:
 
     wxGCDC();
     virtual ~wxGCDC();
-    
+
     /**
        Retrieves associated wxGraphicsContext
     */