functions whose implementation is declared "external". This results in less
    efficient code (all calls will go through a stub), but it prevents interface
    crc changes (-> no recompilations in case of circular dependencies) and it
    also keeps the interface stable (if the external implementation is changed
    afterwards to another external routine or to a local implementation, the
    mangled name of the routine does not change) (mantis #24121)

git-svn-id: trunk@27213 -