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/generic/helpext.h

@@ -111,9 +111,9 @@ public:
 
         @param k
             string to search for, empty string will list all entries
-        
-        @param mode    
-            optional parameter allows the search the index (wxHELP_SEARCH_INDEX) 
+
+        @param mode
+            optional parameter allows the search the index (wxHELP_SEARCH_INDEX)
             but this currently only supported by the wxHtmlHelpController.
 
         @return @true on success