guix package: Rename generation-related procedures.

* guix/scripts/package.scm (profile-numbers): Rename to 'generation-numbers'.
  (previous-profile-number): Rename to 'previous-generation-number'.
  (profile-number): Rename to 'generation-number'.
  (roll-back): Rename 'previous-profile' to 'previous-generation'.

Thank Matthias and Yutaka.

daemon: Use 'int' instead of the internal 'gcry_md_algo_t' type.

Fixes compilation with the forthcoming libgcrypt 1.6.x.
Reported by Matthias Wachs <wachs@net.in.tum.de>
and NIIBE Yutaka <gniibe@fsij.org>.

* nix/libutil/gcrypt-hash.cc (guix_hash_init, guix_hash_final): Use
  'int' as the type of the 'algo' parameter.
* nix/libutil/gcrypt-hash.hh: Update declarations accordingly.

gnu: avahi, dbus: Use /var as $localstatedir.

* gnu/packages/avahi.scm (avahi): Pass '--localstatedir'; add
  'patch/localstatedir'.
* gnu/packages/glib.scm (dbus): Pass '--localstatedir' and
  '--with-session-socket-dir'; add 'patch/localstatedir'.
* gnu/packages/patches/avahi-localstatedir.patch,
  gnu/packages/patches/dbus-localstatedir.patch: New files.
* gnu-system.am (dist_patch_DATA): Add them.

gnu: Move helper code to (gnu system …) modules.

* gnu/packages/grub.scm (<menu-entry>, grub-configuration-file): Move
  to...
* gnu/system/grub.scm: ... here.  New file.
* gnu/packages/linux.scm (<pam-service>, <pam-entry>,
  pam-service->configuration, pam-service->directory,
  %pam-other-services, unix-pam-service): Move to...
* gnu/system/linux.scm: ... here.  New file.
* gnu/system/vm.scm (passwd-file): Move to...
* gnu/system/shadow.scm: ... here.  New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add
  gnu/system/{grub,linux,shadow}.scm.

gnu: vm: Remove potluck hacks.

* gnu/system/vm.scm (example1): Remove.
  (example2): Rename to...
  (system-qemu-image): ... this.  Add 'store' parameter, and remove call
  to 'open-connection'.

gnu: vm: Setup PAM.

* gnu/system/vm.scm (example2): Use 'pam-services->directory'.  Change
  POPULATE to create /etc/pam.d, /etc/login.defs, and /var/run.  Change
  BOOT to spawn syslogd; boot to Bash.  Add inputs.

gnu: vm: Create shadow files with the right format.

* gnu/system/vm.scm (passwd-file): When SHADOW? is true, use the right
  shadow(5) format.  Always add a trailing newline.

linux-initrd: Create /dev/klog and /dev/kmsg.

* guix/build/linux-initrd.scm (make-essential-device-nodes): Make
  /dev/klog and /dev/kmsg.

gnu: linux-initrd: Fix typo.

* gnu/packages/linux-initrd.scm (gnu-system-initrd): Add missing
  argument to 'format' call.

gnu: linux-pam: Add declarative PAM service interface.

* gnu/packages/linux.scm (<pam-service>, <pam-entry>): New record
  types.
  (pam-service->configuration, pam-services->directory,
  unix-pam-service): New procedures.
  (%pam-other-services): New variable.

store: The 'references' parameter of 'add-text-to-store' is now optional.

* guix/store.scm (add-text-to-store): Make 'references' optional.
* tests/store.scm ("dead-paths", "references"): Use 'add-text-to-store'
  with no optional argument.
* doc/guix.texi (The Store): Adjust accordingly.

gnu: isl: Update urls.

* gnu/packages/gcc.scm (isl): Update source and home page url.

gnu: vm: Copy /etc/shadow to the guest.

* gnu/system/vm.scm (example2): Add SHADOW to #:inputs-to-copy.

gnu: vm: Create valid /etc/shadow and /etc/passwd.

* gnu/system/vm.scm (/etc/passwd): Rename to...
  (passwd-file): ... this. Add 'shadow?' keyword parameter.  Change
  format of ACCOUNTS, and fix CONTENTS.
  (example2): Adjust accordingly.  Create both /etc/shadow and
  /etc/passwd, the latter being used by getpwnam(3) & co. when nscd is
  not running.

gnu: vm: Clear timestamps on the imported files, like in the store.

* gnu/system/vm.scm (qemu-image): Clear timestamps on the copied files.

hydra: Support a 'subset' argument.

* build-aux/hydra/gnu-system.scm (%core-packages): New variable.
  (%packages-to-cross-build): Make an alias for %CORE-PACKAGES.
  (hydra-jobs): Check for the 'subset' argument, and honor it for values
  "all" and "core".

gnu: linux-libre: Upgrade to 3.11.

* gnu/packages/linux.scm (linux-libre): Upgrade to 3.11.  Add bc as an
  input.

gnu: grub: Add support for building configuration files.

* gnu/packages/grub.scm (<menu-entry>): New record type.
  (grub-configuration-file): New procedure.
* gnu/system/vm.scm (qemu-image): Remove parameters 'linux',
  'linux-arguments', and 'initrd'.  Add 'grub-configuration' parameter.
  Honor them, and remove grub.cfg generation code accordingly.
  (example2): Use `grub-configuration-file', and adjust accordingly.

doc: Add "Data Types and Pattern Matching" to the Coding Style.

* HACKING (Data Types and Pattern Matching): New section.