bug#20385: Support curved quotes in doc strings

[Eli Zaretskii]

> From: Ivan Shmakov <ivan@siamics.net>
> Date: Thu, 14 May 2015 20:05:53 +0000
> 
> >>>>> Eli Zaretskii <eliz@gnu.org> writes:
> >>>>> From: Ivan Shmakov  Date: Thu, 14 May 2015 07:20:17 +0000
> 
>  >> The ` character is not a quotation mark at all.  In fact, it’s the
>  >> spacing variant of the very same diacritical mark as is shown above
>  >> e in è.
> 
>  > Any references for this?
> 
>       You mean, other than UnicodeData.txt and its derivatives?
>       To quote NamesList.txt, for instance:
> 
> 0060  GRAVE ACCENT
>       * this is a spacing character
>       x (modifier letter grave accent - 02CB)
>       x (combining grave accent - 0300)
>       x (reversed prime - 2035)

Where does it say that it can be combined with some base character as
a diacritical?

I see no decomposition in UnicodeData.txt that has 0060 as its part.