The value TCL_LOCATION_EVAL_LIST in the type field of a CmdFrame appears to
exist only for the sake of taking great pains to make sure that pure list
values remain pure list values.

The value of pure list values is no longer what it once was.  For a long long
time now, any canonical list values have been equally good.  This branch
is Work In Progress eliminating the complication of the additional type value.

Currently some minor botches are breaking execution tracing tests.
Revert the changes that went too far and broke things.
Eliminate the union that is no longer needed.
Drop TCL_LOCATION_EVAL_LIST now that it is unused.
The value TCL_LOCATION_EVAL_LIST in the type field of a CmdFrame appears to
exist only for the sake of taking great pains to make sure that pure list
values remain pure list values.

The value of pure list values is no longer what it once was. For a long long
time now, any canonical list values have been equally good.