emacs: Allow list functions to deal with nil values.

* emacs/guix-list.el (guix-list-get-tabulated-entry): Call functions returning
  column value even for nil values.
  (guix-list-get-one-line): Adjust for accepting nil argument.

guix package: Add '--switch-generation' option.

* guix/scripts/package.scm (switch-to-generation): New procedure.
  (switch-to-previous-generation): Use it.
  (guix-package): Adjust for '--switch-generation' option.
* tests/guix-package.sh: Test it.
* doc/guix.texi (Invoking guix package): Document it.

profiles: Add 'relative-generation'.

* guix/profiles.scm: (relative-generation): New procedure.
  (previous-generation-number): Use it.

profiles: Add condition types for profiles and generations.

Suggested by Ludovic Courtès.

* guix/profiles.scm (&profile-error, &profile-not-found-error,
  &missing-generation-error): New condition types.
* guix/ui.scm (call-with-error-handling): Handle new types.
* guix/scripts/package.scm (roll-back, guix-package): Raise
  '&profile-not-found-error' where needed.

gnu: libarchive: Apply fixes including for CVE-2013-0211.

* gnu/packages/patches/libarchive-CVE-2013-0211.patch,
  gnu/packages/patches/libarchive-fix-lzo-test-case.patch,
  gnu/packages/patches/libarchive-mtree-filename-length-fix.patch: New files.
* gnu-system.am (dist_patch_DATA): Add them.
* gnu/packages/backup.scm (libarchive)[source]: Add patches.

gnu: Add transfig.

* gnu/packages/xfig.scm (transfig): New variable.

gnu: Add xfig.

* gnu/packages/xfig.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add it.

gnu: libjpeg: Upgrade to version 9a.

* gnu/packages/image.scm (libjpeg): Upgrade to version 9a.

gnu: Add imake.

* gnu/packages/xorg.scm (imake): New variable.

syscalls: Accept ENOENT in the 'swapoff' test.

Fixes <http://bugs.gnu.org/18690>.
Reported by Philip Woods <elzairthesorcerer@gmail.com>.

* tests/syscalls.scm ("swapoff, EINVAL/EPERM"): Rename to...
  ("swapoff, ENOENT/EINVAL/EPERM"): ... this.  Add ENOENT to the list of
  possible return values.

Augment '.dir-locals.el' with bug-reference-mode settings.

gnu: Add perl-zip.

* gnu/packages/zip.scm (perl-zip): New variable.

gnu: openssh: Update to 6.7p1.

* gnu/packages/ssh.scm (openssh): Update to 6.7p1.

Add copyright line to gnuzilla.scm.

* gnu/packages/gnuzilla.scm: Add copyright line for Mark H Weaver, which
  should have been added in 74c7af9 (gnu: icecat: Update to 31.1.1).

scripts: Add 'environment' command.

* guix/scripts/environment.scm: New file.
* Makefile.am (MODULES): Add it.
* doc/guix.texi ("Invoking guix environment"): New node.

build: Make sure tests/guix-package.sh doesn't leave anything behind it.

Fixes a regression introduced in commit 300868ba.

* tests/guix-package.sh: Move 'module_dir' definition to the top, and
  "rm -rf" it from the top-most 'trap'.  Remove second use of 'trap'.

doc: Add 'operating-system' reference.

* doc/guix.texi (Using the Configuration System): Add xref to
  "operating-system Reference".
  (operating-system Reference): New section.
  (Networking Services): Add xref to it.

doc: Use @deftp for 'build-machine'.

* doc/guix.texi (Daemon Offload Setup): Use @deftp for 'build-machine'.

gnu: icu4c: Correct error in the binaries' runpath

* gnu/packages/icu4c.scm (icu4c): Apply the RUNPATH to the binaries,
  instead of the libs

ui: Move 'show-manifest-transaction' from (guix profiles).

* guix/profiles.scm: Do not use (guix ui) module.
  (right-arrow, manifest-show-transaction): Move and rename to...
* guix/ui.scm (right-arrow, show-manifest-transaction): ... here.
* tests/profiles.scm ("manifest-show-transaction"): Move to...
* tests/ui.scm ("show-manifest-transaction"): ... here.
  (guile-1.8.8, guile-2.0.9): New variables.
* emacs/guix-main.scm (process-package-actions): Rename
  'manifest-show-transaction' to 'show-manifest-transaction'.
* guix/scripts/package.scm (guix-package): Likewise.

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