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/generic/headerctrlg.h

@@ -50,7 +50,7 @@ public:
 protected:
     virtual wxSize DoGetBestSize() const wxOVERRIDE;
 
-    
+
 private:
     // implement base class pure virtuals
     virtual void DoSetCount(unsigned int count) wxOVERRIDE;