Drop QT4 from master

[Jean-Marc Lasgouttes]

Le 04/01/2021 à 17:25, Thibaut Cuvelier a écrit :
> On Mon, 4 Jan 2021 at 14:56, Jean-Marc Lasgouttes <lasgouttes at lyx.org 
> <mailto:lasgouttes at lyx.org>> wrote:
> 
>     Le 29/12/2020 à 09:42, Yuriy Skalko a écrit :
>      > Seems like boost::regex has the same issues as std::regex:
>      >
>     https://www.boost.org/doc/libs/1_75_0/libs/regex/doc/html/boost_regex/unicode.html
>     <https://www.boost.org/doc/libs/1_75_0/libs/regex/doc/html/boost_regex/unicode.html>
> 
>      >
>      > As I understand the ICU library is the only ultimate solution for
>      > Unicode support.
> 
>     Qt relies on ICU, it would be nice to be able to use the bundled
>     library
>     directly.
> 
> 
> Not all builds of Qt rely on ICU, unfortunately. For macOS and Windows, 
> mostly, Qt uses the native libraries, which allow them to get rid of 
> several megabytes of ICU. That means that binaries for macOS and Windows 
> would have to use custom Qt builds, I'm not sure the maintainers will 
> have the time to do it (it also raises the entry bar for new maintainers).

I stand corrected, then. I would be happy to replace our current iconv 
with something more modern, but I do not trust Qt stuff, which is too 
UTF16-centered and has issues.

JMarc