[Ur] Drop of several orders of magnitude in Techempower benchmarks

[Karn Kallio]

> Hello! I used "git bisect" to find the commit that introduced
> behaviour that causes Ur/Web to fail the Fortunes test in the
> benchmarks. It's commit 5cc729b48aad084757a049b7e5cdbadae5e9e400 from
> November 2018. Unfortunately that's a pretty big squashed commit from
> a PR:
> https://github.com/urweb/urweb/commit/5cc729b48aad084757a049b7e5cdbadae5e9e400
> 
> It'd be great if someone could take a look and see why it strips UTF-8
> output in that benchmark test. Note that the test runs in a Docker
> container, so perhaps it's trying to infer a system-wide i18n setting?
> 
> Once we fix this, we can update the benchmarks repo and solve the
> sorry state of affairs with Ur/Web way down the performance rankings.
> I'd love to see more people active in the community, and things like
> this would help raise awareness of the project.
> 
> Oisín
> 

I suspect this has to do with the difference between LTR and RTL
languages.  A given database, in the fortunes table, may have Arabic
text stored "backwards", and without any markings such as U+200F
RIGHT-TO-LEFT MARK and so the U8_NEXT macro is seeing a trailing byte
of a UTF-8 encoded character and failing to loop.