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

Geoffrey Knauth wrote:
> The fact that it had the right PLT icon, though, required a one-time  
> change telling Mac OS X that PLT owns .plt files, and not  
> GraphicConverter.  The "other" .plt is AutoCAD plot-to-file.

Actually, I think it's Hewlett-Packard Graphics Language, for driving 
their plotters. Googling "PLT" gets me mostly PLT Scheme links, but 
annoyingly enough, the "sponsored" links at the top are about converting 
graphics files. GraphicConverter seems to know about huge numbers of 
file extensions, and is the application that seems to get invoked 
whenever I double-click on a file with an odd extension. --PR