Drop QT4 from master

[Yuriy Skalko]

> Could it be that this is why boost::regex was useful after all? Did we rush too 
> fast in our joy of getting rid of it?
> 
> I do not think that solving issues with crappy compilers involves going all the 
> way in Qt's arms. Qt does have its flaws and bugs, and besides banging our head 
> against the walls, there is not much we can do to cure it. Qt does not follow a 
> standard, it is just Qt. Is it supposed to clear the screen before calling 
> paintEvent? Nobody knows. Does it tell you when the system keyboard is 
> switched? Your guess is as good as mine.
> 
> This is where relying on standards is good. There is correct behavior and 
> incorrect behavior. How do we find a good std::regex implementation for 
> windows? Is there a compiler version that works? Is there an alternative std 
> c++ library we can use? These are better questions than running towards an 
> hypothetical saviour.
> 
> I'm rambling, looks like it is time to go to bed.
> 
> JMarc


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

As I understand the ICU library is the only ultimate solution for 
Unicode support.


Yuriy