[luatex] Bad skips with display math

[Javier Bezos]

> Hans has made a patch that I have commited  on  Sun 23 Jan 2022,  r7484
> 
> New primitive \matheqdirmode.
> By default the short skip detection is not adapted to r2l typesetting and that
> hasn't been the case since the start of the project. Changing it could break
> hacks that users came up with but when you set \matheqdirmode to a positive
> value direction will be taken into account.

Great. Thank you.

Javier