bug#27296: Modular Texlive

[Ricardo Wurmus]

This patch set lays the foundation for a modular Texlive distribution.
Most importantly it adds “texlive-union”, which allows for a custom
subset of Texlive to be defined.

I have tested this successfully on the “fastcap” package.  The reason
why I’m not including a patch to replace “texlive” with “texlive-tiny”
in “fastcap” is that I’m still missing some bibtex packages that are
required by the fastcap documentation for references.

A lot of packages are still missing, but the importer should be enough
to get more things from the Texlive SVN repo packaged.

--
Ricardo

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