emacs: Use package/output type variables where needed.

* emacs/guix-list.el (guix-package-list-type, guix-output-list-describe-type):
  Move to...
* emacs/guix-base.el: ... here.  Rename 'guix-output-list-describe-type' to
  'guix-package-info-type'.
* emacs/guix-info.el (guix-generation-info-insert-number): Use
  'guix-package-list-type'.
* emacs/guix.el (guix-get-show-packages): Use 'guix-package-info-type'.

emacs: Support font-locking.

Avoid breaking highlighting after adding new font-lock keywords.

* emacs/guix-base.el (guix-insert-package-strings): Use 'propertize' instead
  of 'guix-get-string'.
* emacs/guix-info.el (guix, guix-action, guix-file, guix-url,
  guix-package-location, guix-package-name): New button types.
  (guix-info-insert-action-button, guix-info-insert-file-path,
  guix-info-insert-url, guix-package-info-insert-location,
  guix-package-info-insert-full-names,
  guix-package-info-insert-non-unique-text): Adjust for 'guix-insert-button'
  and button types.
  (guix-package-info-name-button): New face.
  (guix-package-info-define-insert-inputs): Use it.  Add new button types.
  (guix-package-info-insert-full-name): Remove.
* emacs/guix-utils.el (guix-get-string): Replace 'face' with 'font-lock-face'.
  (guix-insert-button): Adjust for using button types.

emacs: Fix errors in receiving information.

* emacs/guix-main.scm (package-pattern-transformer,
  output-pattern-transformer): Add fallback 'match' clauses.
  (find-generations): Fix getting generations by IDs.

doc: Use 'define-public' in example package recipe.

* doc/guix.texi (Defining Packages): Use 'define-public' instead of
  'define'.

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

gnu: hurd-headers: Use --build instead of --host.

* gnu/packages/hurd.scm (hurd-headers): Replace '--host' with
  '--build'.

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

gnu: qt-4: Explicitly link with icu.

* gnu/packages/qt.scm (qt-4): Explicitly link with libicui18n, which is
    dlopened by QtCore.so.

gnu: Add Nix.

This commit is dedicated to the Nix project, without which we wouldn't
be hacking all this today.  :-)

* gnu/packages/package-management.scm (nix): New variable.

gnu: Add perl-www-curl.

* gnu/packages/web.scm (perl-www-curl): New variable.

gnu: Add perl-dbi and perl-dbd-sqlite.

* gnu/packages/databases.scm (perl-dbi, perl-dbd-sqlite): New variable.

gnu: mit-scheme: Rename top-level helper.

Suggested by Mark H. Weaver.

* gnu/packages/scheme.scm (source-directory): Rename to...
  (mit-scheme-source-directory): ... this.

gnu: Add graphite2.

* gnu/packages/fontutils.scm (graphite2): New variable.

gnu: mit-scheme: Delete more dangling symlinks for non-x86 systems.

* gnu/packages/scheme.scm (mit-scheme): Delete more dangling symlinks for
    non-x86 systems.

gnu: mit-scheme: Fix source file name for mips64el.

* gnu/packages/scheme.scm (mit-scheme): Fix source file name for
     architectures other than x86_64 and i686.

gnu: phonon: Update to 4.8.0.

* gnu/packages/kde.scm (phonon): Update to 4.8.0.

build: Don't install elisp files when Emacs is unavailable.

* emacs.am (dist_lisp_DATA, nodist_lisp_DATA): Wrap in 'if HAVE_EMACS'.

build: Don't generate Emacs autoloads when Emacs is unavailable.

Reported by Andreas Enge.

* configure.ac: Define 'HAVE_EMACS' Automake conditional.
* emacs.am ($(AUTOLOADS)): Wrap in 'if HAVE_EMACS'.

gnu: mit-scheme: Update to 9.2.

* gnu/packages/scheme.scm (mit-scheme): Update to 9.2.

gnu: libxscrnsaver: Propagate input scrnsaverproto.

* gnu/packages/xorg.scm (libxscrnsaver): Propagate input scrnsaverproto,
    since scrnsaver.h from libxscrnsaver includes saver.h from scrnsaverproto.

gnu: help2man: Update to 1.46.3.

* gnu/packages/man.scm (help2man): Update to 1.46.3.

gnu: gcl: Update to 2.6.11.

* gnu/packages/lisp.scm (gcl): Update to 2.6.11.