[plt-scheme] Emacs tags for MzScheme modules

Built into DrScheme is a module browser and check syntax -- they don't 
do exactly what etags does, but they serve a similar kind of need. Two 
things to try:

  - when you're visiting the "main" file of some project, under the show 
menu, choose "show mdoule browser" and you'll the module dag on your 
right.

  - check syntax and then move you mouse over an imported identifier. 
right click. You'll be able to jump to the `require' that it came from 
and then from there another right-click will send you to the file for 
that require.

Robby