Introduce ly_scm2utf8string, and use it for printing text

Introduce ly_scm2utf8string, and use it for printing text

Before, Text_interface::interpret_string used ly_scm2string, which
runs scm_to_locale_stringn to get at the string. The default locale is
"C", so all Unicode chars are then converted to "?".

[hanwenn, 2020-01-30 10:01:51]

I think this may have lacked sf.net issue. Please review.

[Dan Eble, 2020-01-30 15:03:02]

https://codereview.appspot.com/577440043/diff/553450043/lily/include/lily-gui...
File lily/include/lily-guile.hh (right):

https://codereview.appspot.com/577440043/diff/553450043/lily/include/lily-gui...
lily/include/lily-guile.hh:60: std::string ly_scm2utf8_string (SCM);
The second underscore makes this stand out from the other functions in this
group.

[hanwenn, 2020-01-31 18:01:32]

On 2020/01/30 15:03:02, Dan Eble wrote:
>
https://codereview.appspot.com/577440043/diff/553450043/lily/include/lily-gui...
> File lily/include/lily-guile.hh (right):
> 
>
https://codereview.appspot.com/577440043/diff/553450043/lily/include/lily-gui...
> lily/include/lily-guile.hh:60: std::string ly_scm2utf8_string (SCM);
> The second underscore makes this stand out from the other functions in this
> group.

it does. Do you have a suggestion to improve?

[Dan Eble, 2020-01-31 18:03:25]

On 2020/01/31 18:01:32, hanwenn wrote:
> > The second underscore makes this stand out from the other functions in this
> > group.
> 
> it does. Do you have a suggestion to improve?

ly_scm2utf8string?  ly_scm2utf8?

[hanwenn, 2020-02-01 11:36:19]

rebase; rename.

[hanwenn, 2020-02-01 20:59:02]

On 2020/02/01 11:36:19, hanwenn wrote:
> rebase; rename.

PTAL

[Dan Eble, 2020-02-01 21:03:47]

LGTM

[hanwenn, 2020-03-21 23:03:36]

covered by  

commit f756cab383d91faa6430a1c7f1b041f7855721a9
Author: Jonas Hahnfeld <hahnjo@hahnjo.de>
Date:   Sat Mar 7 19:44:48 2020 +0100

    Issue 5834/2: Use UTF-8 for all conversions to / from Scheme