gnu: xf86-video-intel: Swap input libdrm with mesa.

* gnu/packages/xorg.scm (xf86-video-intel): Drop input libdrm, add input
    mesa.

lint: Allow synopses that start with an abbreviation.

* guix/scripts/lint.scm (starts-with-abbreviation?): New procedure.
  (check-synopsis-style)[check-start-with-package-name]: Use it.
* tests/lint.scm ("synopsis: start with abbreviation"): New test.

lint: Skip starting-article test for the synopses of GNU packages.

* guix/scripts/lint.scm (check-synopsis-style)[check-start-article]:
  Change to (const #t) when PACKAGE matches 'gnu-package?'.

lint: Tolerate sentences that start with a parenthesis or a quote.

* guix/scripts/lint.scm (properly-starts-sentence?): Add (, ", and ' as
  valid beginnings.

lint: Improve check for synopses starting with package name.

* guix/scripts/lint.scm (package-name-regexp): New procedure.
  (check-synopsis-style)[check-start-with-package-name]: Use it instead
  of 'string-prefix-ci?'.
* tests/lint.scm ("synopsis: start with package name prefix"): New test.

gnu: cppunit: Add missing space in description.

* gnu/packages/check.scm (cppunit)[description]: Add missing space.

lint: Simplify no-warnings tests.

* tests/lint.scm ("description: may start with a digit"): Replace
  (not (string-contains exp str)) with (string-null? exp).
  ("description: may start with lower-case package name"): Likewise.
  ("description: end-of-sentence detection with abbreviations"):
  Likewise.
  ("synopsis: may start with a digit"): Likewise.
  ("synopsis: ends with 'etc.'"): Likewise.

gnu: Move pkg-config to 'native-inputs' in various places.

* gnu/packages/glib.scm (libsigc++): Move pkg-config to
  'native-inputs'.
  (glibmm): Likewise.
* gnu/packages/mpd.scm (mpd): Likewise.
* gnu/packages/package-management.scm (guix-0.7): Likewise.
* gnu/packages/sdl.scm (sdl-net): Likewise.
  (sdl-ttf): Likewise.
* gnu/packages/xiph.scm (vorbis-tools): Likewise.

emacs: Add 'guix-prettify'.

* emacs/guix-prettify.el: New file.
* emacs.am (ELFILES): Add it.
* doc/emacs.texi (Emacs Prettify): New node.
* doc/guix.texi (Features): Mention it.

services: xorg: Allow users to specify a list of resolutions.

* gnu/services/xorg.scm (xorg-start-command): Add #:resolutions
  parameter and 'screen-section' procedure.  Use it.
* doc/guix.texi (X Window): Adjust accordingly.

services: xorg: Allow users to specify the drivers to use.

* gnu/services/xorg.scm (xorg-start-command): Add #:drivers parameter.
  Add 'device-section' procedure, and use it in 'xserver.conf'.
* doc/guix.texi (X Window): Document it.

services: xorg: Fix typo in xserver.conf.

* gnu/services/xorg.scm (xorg-start-command)[xserver.conf]: Add missing
  double-quote in AllowMouseOpenFail.

gnu: Add xf86-video-modesetting.

* gnu/packages/xorg.scm (xf86-video-modesetting): New variable.
* gnu/services/xorg.scm (xorg-start-command)[xserver.conf]: Add
  ModulePath line for XF86-VIDEO-MODESETTING, commented out.

vm: Factorize common QEMU options.

* gnu/system/vm.scm (common-qemu-options): New procedure.
  (system-qemu-image/shared-store-script): Use it.

vm: Remove unused procedure.

* gnu/system/vm.scm (input->name+output): Remove.  Its last user
  disappeared in commit b53833b.

tests: Avoid Bash extension in 'tests/guix-lint.sh'.

* tests/guix-lint.sh: Remove redundant and non-portable 'export'.

gnu: ots: Make sure the shared library has the '.so' extension.

Fixes <http://bugs.gnu.org/18521>.

* gnu/packages/ots.scm (ots)[arguments]: Add #:phases.

gnu: Synchronize descriptions with the Womb.

Note: some of these changes undo bits of 35b9e4232.

* gnu/packages/base.scm, gnu/packages/gperf.scm, gnu/packages/guile.scm,
  gnu/packages/libidn.scm, gnu/packages/miscfiles.scm,
  gnu/packages/telephony.scm: Adjust synopses and descriptions as
  suggested by 'make sync-descriptions'.

system: Define 'INFOPATH' in /etc/profile.

* gnu/system.scm (etc-directory)[bashrc]: Set 'INFOPATH'.

gnu: guix: Update development snapshot.

* gnu/packages/package-management.scm (guix-devel): Update to commit
  84934f4.