gnu: Add r-cubature.

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

gnu: Add r-urca.

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

gnu: Add r-fractal.

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

gnu: Add r-extradistr.

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

gnu: Add r-tsa.

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

gnu: Add r-wmtsa.

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

gnu: Add r-tseries.

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

gnu: Add r-quantmod.

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

gnu: Add r-sapa.

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

gnu: Add r-ifultools.

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

gnu: Add r-splus2r.

* gnu/packages/cran.scm (r-splus2r): New variable.

gnu: Add r-leaps.

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

gnu: Add r-ttr.

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

gnu: Add r-rbiofabric.

* gnu/packages/graph.scm (r-rbiofabric): New variable.

gnu: Add r-sna.

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

gnu: Add r-statnet-common.

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

gnu: Add r-network.

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

gnu: nghttp2: Update to 1.31.0.

* gnu/packages/web.scm (nghttp2): Update to 1.31.0.

gnu: libpsl: Update to 0.20.1.

* gnu/packages/web.scm (libpsl): Update to 0.20.1.

gnu: zerofree: Update to 1.1.1.

* gnu/packages/linux.scm (zerofree): Update to 1.1.1.