[LyX/master] Implement variable size bigops

[Enrico Forestieri]

On Fri, Jul 17, 2020 at 10:32:09PM +0200, Jean-Marc Lasgouttes wrote:
> 
> This is something that has been bugging me for some time. Look at the file
> in attachment to see what the effect is.

Yes, it looks better. However, it also makes more evident that the
lower limit of an integral is badly placed. In general, the limits
of an integral were better placed until lyx 2.2 and somewhat broken
starting from 2.3.

-- 
Enrico