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/msw/dc.h

@@ -125,7 +125,7 @@ public:
     }
 
     void* GetHandle() const wxOVERRIDE { return (void*)GetHDC(); }
-    
+
     const wxBitmap& GetSelectedBitmap() const wxOVERRIDE { return m_selectedBitmap; }
     wxBitmap& GetSelectedBitmap() wxOVERRIDE { return m_selectedBitmap; }