[plt-scheme] new version of prog langs text (also making the collection work on r301.5 from svn)

> Anyway, I didn't know I could enter a URL (instead of a filename) for
> "install *.plt file". Maybe the real answer is that this is what people
> should be doing.

You know, if you look at the software section of the book's page, it
says (and has always said)

  In DrScheme's File menu, select Install .plt File... and enter the
  URL of the file appropriate to your software version number:

Anyway, I've added some text recommending that people use this option
instead of downloading the file directly.  Thanks for helping us
identify this problem.

Danny, thanks for the "bug" report.

Shriram