backing out the TCL_EVAL_REDIRECT changes, orthogonal
more NRE abstraction
more info hiding: stop using the macro version of NRAddCallback
code reorg, trying to make it clearer who needs to know what about NRE internals
adding new file, forgotten in last commit
merge trunk
tailcall now running in a simpler model, with no eval-flags and no nre-stack rewriting.
bring in improvs from trunk
merge trunk
merge trunk