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.

gnu: python-webencodings: Fix typo in description.

* gnu/packages/python-web.scm (python-webencodings)[description]: Fix typo.

gnu: delta: Remove redundant code.

* gnu/packages/debug.scm (delta)[arguments]: Remove unneeded MKDIR-P
calls.

gnu: perl-mozilla-ca: Update to 20180117.

* gnu/packages/perl.scm (perl-mozilla-ca): Update to 20180117.

gnu: perl-test-harness: Update to 3.41.

* gnu/packages/perl-check.scm (perl-test-harness): Update to 3.41.

gnu: highlight: Don't hard-code Lua version.

* gnu/packages/pretty-print.scm (highlight)[arguments]: Construct the
Lua prefix programatically instead of hard-coding it.

gnu: highlight: Update to 3.42.

* gnu/packages/pretty-print.scm (highlight): Update to 3.42.

gnu: ghc-abstract-deque: Fix typos in description.

* gnu/packages/haskell.scm (ghc-abstract-deque)[description]: Fix typos.

gnu: qscintilla: Use HTTPS home page.

* gnu/packages/qt.scm (qscintilla)[home-page]: Use HTTPS.

gnu: fortify-headers: Update to 0.9.

* gnu/packages/suckless.scm (fortify-headers): Update to 0.9.