gnu: r-devtools: Update to 1.13.4. * gnu/packages/statistics.scm (r-devtools): Update to 1.13.4.
gnu: r-mclust: Update to 5.4. * gnu/packages/statistics.scm (r-mclust): Update to 5.4.
gnu: r-rcppeigen: Update to 0.3.3.3.1. * gnu/packages/statistics.scm (r-rcppeigen): Update to 0.3.3.3.1.
gnu: r-car: Update to 2.1-6. * gnu/packages/statistics.scm (r-car): Update to 2.1-6.
gnu: r-sn: Update to 1.5-1. * gnu/packages/statistics.scm (r-sn): Update to 1.5-1.
gnu: r-openssl: Update to 0.9.9. * gnu/packages/statistics.scm (r-openssl): Update to 0.9.9.
gnu: r-hms: Update to 0.4.0. * gnu/packages/statistics.scm (r-hms): Update to 0.4.0. [propagated-inputs]: Add r-rlang and r-pkgconfig.
gnu: r-dendextend: Update to 1.6.0. * gnu/packages/cran.scm (r-dendextend): Update to 1.6.0.
gnu: r-recipes: Update to 0.1.1. * gnu/packages/cran.scm (r-recipes): Update to 0.1.1. [propagated-inputs]: Add r-broom and r-matrix.
gnu: Add r-broom. * gnu/packages/cran.scm (r-broom): New variable.
gnu: Add r-psych. * gnu/packages/cran.scm (r-psych): New variable.
gnu: mongodb: Use scons-build-system. * gnu/packages/databases.scm (mongodb): Switch to scons-build-system.
gnu: klick: Use scons-build-system. * gnu/packages/music.scm (klick): Switch to scons-build-system.
gnu: pingus: Use scons-build-system. * gnu/packages/games.scm (pingus): Switch to scons-build-system.
gnu: godot: Use scons-build-system. * gnu/packages/game-development.scm (godot): Switch to scons-build-system.
gnu: metabat: Use scons-build-system. * gnu/packages/bioinformatics.scm (metabat): Switch to scons-build-system.
gnu: serf: Use scons-build-system. * gnu/packages/web.scm (serf): Switch to scons-build-system.
gnu: gpick: Use scons-build-system. * gnu/packages/image.scm (gpick): Switch to scons-build-system.
gnu: linuxdcpp: Use scons-build-system. * gnu/packages/direct-connect.scm (linuxdcpp): Switch to scons-build-system.
build-system: Add scons-build-system. * guix/build-system/scons.scm: New file. * guix/build/scons-build-system.scm: New file. * Makefile.am (MODULES): Register them. * doc/guix.texi (Build Systems): Add scons-build-system.