fix signed/unsigned mismatch
fix unsigned negation
fix signed/unsigned mismatch
fix signed/unsigned mismatch
correct fix to the natcmp_ex

Till now the actualy length diff between the strings was under
circumstances returned. Whereby for a compare function only return
values of (1, 0, -1) make sense. Thus the old behavior isn't
present anymore, natcmp_ex now behaves as a standard compare function.