Add bzip2 as a dependency to base R.
Switch from installing the R packages from tar files to installing from
the extracted directory. This is more in line with a standard install
and also allows installing from VCS.
Use the Bioconductor version for BiocGenerics and future Bioconductor
packages. Suffix the package with 'bioc-$version' to indicate which
Bioconductor release the package is a part of. This is actually more
important than the actual version attached to individual packages
although those are subject to change within the Bioconductor branch.
