gnu: Add python-gridmap.

* gnu/packages/python.scm (python-gridmap, python2-gridmap): New variables.

gnu: Add python-psutil.

* gnu/packages/python.scm (python-psutil, python2-psutil): New variables.

gnu: Add python-rpy2.

* gnu/packages/python.scm (python-rpy2, python2-rpy2): New variables.

gnu: gcc-5: Update to 5.2.0.

* gnu/packages/gcc.scm (gcc-5): Update to 5.2.0.  Remove
  gcc-arm-link-spec-fix.patch from patches.

gnu: gcc-5.1, gcc-toolchain-5.1, libstdc++-doc-5.1: Rename to *-5.

This reflects the new version numbering scheme for GCC 5 and up.
See <https://gcc.gnu.org/develop.html>.

* gnu/packages/gcc.scm (gcc-5.1): Rename to ...
  (gcc-5): ... this.
  (libstdc++-doc-5.1): Rename to ...
  (libstdc++-doc-5): ... this, and use gcc-5.
* gnu/packages/commencement.scm (gcc-toolchain-5.1): Rename to ...
  (gcc-toolchain-5): ... this, and use gcc-5.
* build-aux/hydra/gnu-system.scm (%core-packages): Use gcc-5.

Merge branch 'core-updates'

system: Default to Linux-libre 4.0.

* gnu/system.scm (<operating-system>)[kernel]: Change default to
  LINUX-LIBRE-4.0.

Merge branch 'master' into core-updates

gnu: Add python-feedgenerator.

* gnu/packages/python.scm (python-feedgenerator, python2-feedgenerator): New
  variables.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

gnu: Add gnu-c-manual.

* gnu/packages/gcc.scm (gnu-c-manual): New variable.

gnu: metabat: Minor tweaks.

* gnu/packages/bioinformatics.scm (metabat)[arguments]: Fix indentation in
  'fix-includes' phase.
  [license]: Fix misspelling.

gnu: Add metabat.

* gnu/packages/bioinformatics.scm (metabat): New variable.

gnu: lxappearance: Add missing slash.

* gnu/packages/lxde.scm (lxappearance)[source]: Add missing slash.

gnu: emacs-mmm-mode: Use gnu-build-system.

* gnu/packages/emacs.scm (emacs-mmm-mode): Replace melpa-stable URL with
  the github URL and use 'gnu-build-system' instead of
  'emacs-build-system'.  Fix typo (add missing space before the
  description).

gnu: mariadb: Update to 10.0.20.

* gnu/packages/databases.scm (mariadb): Update to 10.0.20.

gnu: guile-opengl: Install compiled modules in the correct place.

* gnu/packages/gl.scm (guile-opengl): Install compiled modules in the same
  directory as the source modules.

gnu: cross-base: Distinguish cross Linux headers from native headers.

Commit c6d33a9 provided an incorrect fix, whereby the "linux-headers" key
would be used twice in %BUILD-INPUTS and the 'set-cross-path' phase would
refer to the first one of them, which happened to be the native headers, and
not the target headers.  This patch solves the problem by removing the
ambiguity.

* gnu/packages/cross-base.scm (cross-gcc-arguments)[set-cross-path]: Remove to
  "xlinux-headers" instead of "linux-headers".
  (cross-gcc): When LIBC is true, add explicit "xlinux-headers" input, taken
  from LIBC's propagated inputs.

gnu: ninja: Do not report files with mtime = 0 as missing.

This is a followup to 47f315a.

* gnu/packages/patches/ninja-zero-mtime.patch: New file.
* gnu-system.am (dist_patch_DATA): Add it.
* gnu/packages/ninja.scm (ninja)[source]: Reinstate 'patches' field and add
  this patch.
  [arguments]: Remove 'apply-ninja-tests.patch' phase.

gnu: rapidjson: Build without -Werror.

* gnu/packages/web.scm (rapidjson)[source]: Add 'snippet'.

gnu: crda: Add forgotten patch.

This file should have been added as part of commit cc205da.

* gnu/packages/patches/crda-optional-gcrypt.patch: New file.
* gnu-system.am (dist_patch_DATA): Add it.