Put in initial fix for id->msg so that it will not violate the (-> syntax
string) contract of syntax->source-info when it is not a syntax object.
Still need to investigate why we are getting #f or '(#f #f) there and if that
should be happening.
  nanopass/meta-parser.rkt

Updated a few details in the unit tests, including a couple fixes to fixes.
Can now walk through the first 33% of the file without errors.
  tests/unit-tests.rkt