bug#25987: 25.2; support gcc fixit notes

[Eli Zaretskii <eliz@gnu.org>]

> From: Richard Stallman <rms@gnu.org>
> CC: tom@tromey.com, 25987@debbugs.gnu.org
> Date: Wed, 08 Mar 2017 23:20:20 -0500
> 
>   > > The reason is compatibility with clang, which had this option first.
>   > > http://releases.llvm.org/3.8.0/tools/clang/docs/UsersManual.html#cmdoption-fdiagnostics-parseable-fixits
> 
>   > Thanks.  So maybe GCC should have a similar option, named differently,
>   > which would report in characters.
> 
> I am not sure whether that is serious or in jest.

It's serious.

> Do you have a serious suggestion for a change in GCC?
> If so, what would it be?

Like I wrote: I think GCC should introduce a (differently-named)
option which would report positions inside a line in terms of
characters, not bytes.  Reports in bytes require applications that use
these hints to somehow preserve or reconstruct the original encoding
of the file as it was presented to the compiler, something that could
be a pain.

I understand why GCC developers wanted to be bug-compatible with
clang, to allow the various front-ends use GCC without any changes,
but it sounds wrong for GCC to be forever stuck with this bad design
decision made by clang.