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/propgrid/editors.h

@@ -427,7 +427,7 @@ public:
     class wxSampleMultiButtonEditor : public wxPGTextCtrlEditor
     {
         wxDECLARE_DYNAMIC_CLASS(wxSampleMultiButtonEditor);
-        
+
     public:
         wxSampleMultiButtonEditor() {}
         virtual ~wxSampleMultiButtonEditor() {}