hydra: Change 'qemu-jobs' to return name/thunk pairs.

* build-aux/hydra/gnu-system.scm (qemu-jobs)[->job]: Change the cdr to a
  thunk.

hydra: Add 'qemu-image' job.

* build-aux/hydra/demo-os.scm: New file.
* Makefile.am (EXTRA_DIST): Add it.
* build-aux/hydra/gnu-system.scm (qemu-jobs): New procedure.
  (hydra-jobs): Use it.
* guix/scripts/system.scm (read-operating-system): Export.

guix package: Fix indentation of packages to remove.

* guix/scripts/package.scm (show-what-to-remove/install): Add space when
  showing packages to remove.

gnu: Add 'gcc-toolchain'.

* gnu/packages/base.scm (gcc-toolchain): New procedure.
  (gcc-toolchain-4.8): New variable.

doc: Add "Build Systems" section.

* doc/guix.texi (Defining Packages): Add 'arguments' field in the
  example; update 'synopsis' and 'description'.  Remove most of the
  description of 'build-system', and instead reference to the "Build
  Systems" node.  Briefly describe 'arguments' field, and remove more
  elaborate description.  Add cross-reference to "Packaging Guidelines".
  (Build Systems): New node.
  (Packaging Guidelines): Mention '--log-file'.

gnu: qemu: Change multiple-SMB-share patch to /gnu/store.

* gnu/packages/patches/qemu-multiple-smb-shares.patch: Change
  "/nix/store" to "/gnu/store".

gnu: Add clusterssh

* gnu/packages/admin.scm (clusterssh): New variable

gnu: Add perl-x11-protocol

* gnu/packages/xorg.scm (perl-x11-protocol): New variable

gnu: Add perl-tk

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

gnu: net-base: Upgrade to 5.2.

* gnu/packages/admin.scm (net-base): Upgrade to 5.2; use
  'mirror://debian'.

gnu: shadow: Take the source from Git.

* gnu/packages/admin.scm (shadow)[source]: Use the git repo.

gnu: guile-ssh: Use libssh 0.5.5 patched for CVE-2014-0017.

* gnu/packages/patches/libssh-CVE-2014-0017.patch: New file.
* gnu-system.am (dist_patch_DATA): Add it.
* gnu/packages/ssh.scm (libssh-0.5): New variable.
  (guile-ssh): Use it.

ui: Improve reporting of 'system-error' exceptions.

* guix/ui.scm (call-with-error-handling): Change 'system-error' handler
  to display the error message as it was raised.

gnu: xpdf: Build sequentially.

* gnu/packages/pdf.scm (xpdf)[arguments]: Add #:parallel-build? #f.

gnu: lsh: Build with Readline 6.2.

* gnu/packages/lsh.scm (lsh): Use READLINE-6.2 instead of READLINE.

gnu: gdb: Disable tests.

* gnu/packages/gdb.scm (gdb): Disable tests.

gnu: valgrind: Adjust patch for glibc 2.19.

* gnu/packages/patches/valgrind-glibc.patch: s/2.18/2.19/.

union: Ensure that the output is always a directory.

Fixes the creation of single-package profiles, reported by Ludovic Courtès.

* guix/build/union.scm (union-build): Add new internal procedure
  'union-of-directories' that always creates a directory, containing the code
  previously used only to merge multiple directories.  Call it from the
  multiple-directory case in 'union' and from the top-level 'union-build'.

pki: Introduce 'write-acl', and fix wrong conversion in 'ensure-acl'.

* guix/pki.scm (write-acl): New procedure.
  (ensure-acl): Use it.  Fixes a regression introduced in 39831f1,
  whereby 'ensure-acl' would yield a wrong-type-arg error.
* guix/scripts/archive.scm (authorize-key): Use 'write-acl'.

build: Remove now useless Boost headers.

* daemon.am (libformat_headers): Remove 6 nix/boost files that were
  removed in Nix commit 1c2550a2ae826c422cf6d34f1c5c3e687474929d.