bug#20385: [PROPOSED PATCH] Support quoting 'like this' in doc strings

[Drew Adams <drew.adams@oracle.com>]

I said this, which is not clear:

> If this were HTML or XML (or even JSON) then we would not be trying
> to sacrifice one of the first two for the third.  We would simply
> adopt an unmistakable tag for code quoting.

No doubt we do have a similarly unmistakable tag for code quoting,
in TexInfo.

That tag is transformed to `...' in Emacs Info.  If it were transformed
to ‘...’ instead then we would lose the distinction between single-quoted
ordinary text and quoted code.  That's all.

And of course in help (e.g. `C-h f') and in Emacs-Lisp comments and doc
strings, there is no TexInfo representation.

Users should be able to search for a code term foo and not also hit
ordinary text occurrences of foo.  That is approximately possible
today.  And it is simple today to (reasonably, if imperfectly) tell
font-lock to highlight `...' occurrences (as it would be for ‘...’).

In some XML-based editors that provide a WSIWYG view, users can
search specially for a given element (e.g. <CodeInline>) or one with
a given attribute value, while remaining in WYSIWYG.  But that is
a separate search capability from regexp or simple text search in
the same editors.  In Emacs you can easily search for `...' occurrences
and pretty much find what you are looking for.