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/qt/mdi.h

@@ -75,7 +75,7 @@ class WXDLLIMPEXP_CORE wxMDIClientWindow : public wxMDIClientWindowBase
 {
 public:
     wxMDIClientWindow();
-    
+
     virtual bool CreateClient(wxMDIParentFrame *parent, long style = wxVSCROLL | wxHSCROLL);
     wxDECLARE_DYNAMIC_CLASS(wxMDIClientWindow);
 };