makeinfo should quote 'like this' instead of `like this'

[Paul Eggert]

In response to the recent change to the GNU coding standards, which
now encourages quoting 'like this' (with apostrophes) or "like this"
(with double-quotes) instead of `like this' (with acute accent and
apostrophe) when quoting in ASCII, we've gone through Gnulib and
have replaced most instances of the old quoting style with the new one.
One area that still needs work is the output of 'makeinfo'.

One example is the gnulib file install.texi
<http://git.savannah.gnu.org/gitweb/?p=gnulib.git;a=blob;f=doc/install.texi>.
In GNU texinfo 4.13, when 'makeinfo --no-validate install.texi' sees this:

   see the @file{README} file

it generates this:

   see the `README' file

We want it to generate this instead, with apostrophes:

   see the 'README' file

And in general, we want the glyph for left single quotation mark to be
the ASCII apostrophe, when generating ASCII output.  Of course when
generating UTF-8 makeinfo can continue to use the Unicode directed
single quotation marks.

Currently we get the effect we want by transliterating ` to ' in
makeinfo's output, but obviously this won't work in general as
sometimes ` is what's wanted (e.g., in example code).

I suggest modifying makeinfo so that it generates quotes 'like this'
rather than `like this', in situations such as the above.  If you
like, I can try to code up a patch along these lines.