[LyX/master] Reduce the amount of needed boost headers

[Enrico Forestieri]

On Mon, Dec 14, 2020 at 01:20:31AM +0200, Yuriy Skalko wrote:
> > We collided on the fly ;)
> > 
> > -- 
> > Enrico
> 
> 
> That's unreal ;)

I meant that we were trying to commit the same change at the same time ;)

-- 
Enrico