[9d61624b3d]: Stop crashes when emptying the superclass slot.
Deal with the elaborate rip-apart-a-metaclass case as well.
[3611643fff]: Support TclOO in autoload mechanism.
Mark unixforkevent-1.1 nonPortable, until proven on more platforms.
Mark unixforkevent-1.1 nonPortable, until proven on more platforms. 
Make sure that when testing for pthread_atfork the thread library is taken into account.
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.
Add assertions that will guide and protect more discovery of dead code for elimination.
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.
All use of the evalFlag value TCL_EVAL_CTX is unused by the code and
unreachable by extensions.  This checkin removes all the code supporting
that flag value.

The consequence is that all the calls to TclNREvalObjEx() and its callers
that are currently choosing not to pass the TCL_EVAL_DIRECT flag in when
they pass in a non-NULL invoker will no longer be free to change their
mind.  That might be reason not to adopt this change.
Add comment stating new limitation on Tcl(NR)EvalObjEx() interface.
Replace potentially memleak creating safety check of a "cannot happen"
condition with an assertion.
Test for TclContinuationsGet() usage, and simplifications.
Remove Tcl_Preserve support for ContLineLoc values.  It's not needed.
This allows the clLoc field of CompileEnv struct to go away too.
Many simplifications to the TIP 280 machinery.
   * Removed support for non-NULL invoker when TCL_EVAL_DIRECT requested.
   * Eliminated TCL_EVAL_CTX eval flag.
   * Removed Tcl_Preserve-ability of ContLineLoc pointers.
   * Removed clLoc field of CompileEnv struct.
Give (objc, objv) their own ride from enter to leave traces.
Revise GetCommandSource() to return a normal Tcl_Obj value.
Revised GetCommandSource() can (and thus should) return a normal zero
refcount value.