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/datectrl.h

@@ -87,7 +87,7 @@ public:
        Default constructor.
     */
     wxDatePickerCtrl();
-    
+
     /**
         Initializes the object and calls Create() with all the parameters.
     */