debugging is disabled:
* got rid of the `stacktrace-runtime-name' hack in "rep.ss", replace
it by a more reliable capture of the context, and later cut the
stack according to that specific context.
* the cutting is done if possible, no need for the "ACK!" error
message if no cutting point is found.
* rename `with-stacktrace-name' -> `with-stack-checkpoint'
* add this to "module-language.ss" too, to avoid including it in error
messages.
svn: r14777
f51c6bbe64