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/app.h

@@ -104,7 +104,7 @@ public:
 
     // Called before the first events are handled, called from within MainLoop()
     virtual void OnLaunched();
-    
+
     // This is called by wxEventLoopBase::SetActive(): you should put the code
     // which needs an active event loop here.
     // Note that this function is called whenever an event loop is activated;