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

The theory behind media (MIME) types is that they should be used to
identify the resource type, not the file extension. So, in principle,
if you have a URL like

http://wherever.org/some-html.txt

and some-html.txt is actually, HTML, then if the media type in the HTTP
header is text/html, then the client (browser) knows that it is HTML
and presents it accordingly. 

I've never run into the problem you describe with .plt files, and it
may be that I never installed the CAD application, but I would expect
that metadata associated with the file would indicate that it's not an
image. 

I had thought a generic media type like application/octet-stream would
be nice because it would at least allow downloading the file with a
single click. In fact, that's the behavior I expected, not having the
installer launch automatically. (This was under Windows, but even on my
PowerBook, clicking on the .plt files automatically launches the installer.)

===
Gregory Woodhouse  <gregory.woodhouse at sbcglobal.net>
"All truth passes through three stages: First, it is ridiculed.
Second, it is violently opposed. Third, it is accepted as
being self-evident."
--Arthur Schopenhauer