Roll back smallcptr.char.mix change to Filename etc.?

[Michael Smith <smith@xml-doc.org>]

Is there an RFE for the "switch cptr.char.mix to smallcptr.char.mix on
Filename etc." change between 3.1 and 4.x? If not, can anybody
articulate the rationale for it?

It seems like it might need to be rolled back, at least on some
elements, like Filename at least. 

That change has caused unforeseen problems, like the fact that in 4.x,
you've got no way to mark up the following (from the Emacs man page):

   /usr/lib/emacs/$VERSION/src

That is, you're out of luck if you want to have to mark up a pathname
with an environment variable in the middle of it.

Nik Clayton pointed out the problem a while back:

  http://lists.oasis-open.org/archives/docbook/200101/threads.html#00059

Norm responded at that time that "This may be evidence that we reduced
the content model of filename (and perhaps other elements) too far."

The issue has since risen independently on the KDE-docbook list,
probably elsewhere too.