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/evtloop.h

@@ -324,7 +324,7 @@ public:
     @class wxGUIEventLoop
 
     A generic implementation of the GUI event loop.
-    
+
     @library{wxbase}
     @category{appmanagement}
 */