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.

include/wx/dcgraph.h

@@ -32,7 +32,7 @@ public:
     wxGCDC( const wxEnhMetaFileDC& dc );
 #endif
     wxGCDC(wxGraphicsContext* context);
-    
+
     wxGCDC();
     virtual ~wxGCDC();