0.8.0.41: "Hunting on worms, part II"

0.8.0.41: "Hunting on worms, part II"
        Insertion of type check on a function result continuation
        prevents tail call optimisation, so:
        * pathwise eliminate unnecessary type checks;
        * disable unsafe CAST insertion on function results.

        Now Paul Dietz' test suite finishes with "83 out of 12565
        total tests failed".