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

[Pavel Sanda]

On Mon, Dec 28, 2020 at 07:21:59PM +0100, Jean-Marc Lasgouttes wrote:
> >BTW after all the boost related changes, what are the dependencies needed for people using external boost?
> >E.g. current 2.3.x debian build dependencies are libboost-filesystem-dev, libboost-iostreams-dev, libboost-regex-dev, libboost-signals-dev, libboost-test-dev.
> >Can some of these be removed now?
>
> Nothing is needed for running LyX. We do not use any library. I do not know what is the dependency to have only the boost headers, maybe libboost-dev.

I'll check the details, thanks for the info. Pavel