bug#25462: Out of date doc string for "`".

[John Mastro]

Noam Postavsky <npostavs@users.sourceforge.net> wrote:
> On Mon, Jan 16, 2017 at 4:30 PM, Alan Mackenzie <acm@muc.de> wrote:
>> Hello, Emacs.
>>
>> The doc string for "`" has become partial.
>>
>> It fails to mention that "`" has a radically different meaning when used
>> in certain parts of a `pcase', and probably quite a few other similar
>> macros.
>
> I don't think that makes sense. Similarly, we don't add a mention of
> `cl-loop's use of `if' in the docstring of `if', because that's not
> part of the `if' special form. It's just a use of `if' as a plain
> symbol.

Since the misunderstanding is believing that "`" is more special than it
is, maybe something calling out its ordinariness could be appropriate
(and throw in a reference to pcase as an example?)

I don't think this is great, but, as an example:

    Note that `\\=`' is any ordinary Lisp symbol and thus may be treated
    as data or given different meanings in particular contexts. For
    instance, it has a special meaning inside `pcase' patterns.