Updated URL

The new URL is http://www.math.mcgill.ca/barr/lambek/pdffiles/. I have added a few items, deleted a couple that were duplicates, and essentially tightened it up. There were a couple of case clashes since Linux is case sensitive and Windows isn't so the link was broken. If there are any further problems with the papers, please let me know and I will repair them. Michael [For admin and other information see: http://www.mta.ca/~cat-dist/ ]