0.9.17.5:

        The debugger tends to not show all variables regardless of the
        optimization policy. Fix the most common reason for that happening.

        * When compiling with a high debug quality, don't do substitution for
          variables that are only used once.
        * Except for variables introduced in DEFTRANSFORM inline
          lambdas, since they're not going to very interesting for the
          debugger.