gnu: Add r-lmtest.

* gnu/packages/cran.scm (r-lmtest): New variable.

gnu: Add r-extremes.

* gnu/packages/cran.scm (r-extremes): New variable.

gnu: Add r-distillery.

* gnu/packages/cran.scm (r-distillery): New variable.

gnu: Add r-lmoments.

* gnu/packages/cran.scm (r-lmoments): New variable.

gnu: Add r-rmtstat.

* gnu/packages/cran.scm (r-rmtstat): New variable.

gnu: Add r-rook.

* gnu/packages/web.scm (r-rook): New variable.

gnu: Add r-sp.

* gnu/packages/cran.scm (r-sp): New variable.

gnu: Add r-proxy.

* gnu/packages/cran.scm (r-proxy): New variable.

gnu: Add r-ggally.

* gnu/packages/cran.scm (r-ggally): New variable.

gnu: Add r-progress.

* gnu/packages/cran.scm (r-progress): New variable.

gnu: Add r-reshape.

* gnu/packages/cran.scm (r-reshape): New variable.

gnu: Add r-prettyunits.

* gnu/packages/cran.scm (r-prettyunits): New variable.

gnu: Add r-ffbase.

* gnu/packages/cran.scm (r-ffbase): New variable.

gnu: Add r-ff.

* gnu/packages/cran.scm (r-ff): New variable.

gnu: Add r-fastmatch.

* gnu/packages/cran.scm (r-fastmatch): New variable.

gnu: Add r-getoptlong.

* gnu/packages/cran.scm (r-getoptlong): New variable.

gnu: Add r-dendextend.

* gnu/packages/cran.scm (r-dendextend): New variable.

gnu: Add r-compare.

* gnu/packages/cran.scm (r-compare): New variable.

gnu: Add r-png.

* gnu/packages/image.scm (r-png): New variable.

gnu: Add r-powerlaw.

* gnu/packages/cran.scm (r-powerlaw): New variable.