Hi Guix,

Bioconductor is a large, popular repository of R packages for
bioinformatics.  It has coordinated, versioned releases (latest stable
release is 3.2).

The attached patches generalise the existing procedures used by the CRAN
importer, so that with only little effort importers for other R
repositories are possible.  The last patch adds an importer for the
Bioconductor repository.

Imported package expressions now also contain a package property
“r-repository”, which is either the symbol “cran” or the symbol
“bioconductor”.  This is also checked in the predicates “cran-package?”
and “bioconductor-package?” used by the updaters.

The first two patches in this series are actually unrelated: the first
fixes an annoying bug in the CRAN importer; the second corrects an
outdated claim in the CRAN importer’s documentation.

~~ Ricardo