add some debugging information into the module language test suite

specifically, when tests fail and there is an error icon in the REPL,
then go find the stack associated with it and print it out
fix a non-buggy set!-before-initialization in syntax-browser

What appears to be happening is that the fields path and next-push
are state variables on this class that are initialized and then used
only during the dynamic-extent of syntax-object->datum/record-paths
and of the pretty-printing code.

So, before the check was in place, they were initialized and used
before the 'path' field was initialized, but by the time the path
field was initialized, the value was junk (not going to be used again)
but it still raised an error