utils: 'current-source-directory' resolves relative file names at run time.

* guix/utils.scm (absolute-dirname): New procedure.
(current-source-directory): Emit code to use it instead of calling
'search-path'.

store: 'register-path' no longer swallows 'system-error' exceptions.

* guix/store.scm (register-path): Do not catch 'system-error'.

services: Add 'gc-root-service-type'.

* gnu/services.scm (gc-roots->system-entry): New procedure.
(gc-root-service-type): New variable.

gnu: libxslt: Replace with 1.1.29 [fixes CVE-2016-{1683,1684}].

* gnu/packages/xml.scm (libxslt)[replacement]: New field.
(libxslt/fixed): New variable.

gnu: synthv1: Update to 0.7.5.

* gnu/packages/music.scm (synthv1): Update to 0.7.5.

gnu: Add lbzip2.

* gnu/packages/compression.scm (lbzip2): New variable.

gnu: Add emacs-multiple-cursors.

* gnu/packages/emacs.scm (emacs-multiple-cursors): New variable.

gnu: Add guile-sqlite3.

* gnu/packages/guile.scm (guile-sqlite3): New variable.

gnu: bluez: Install 'org.bluez.obex.service' and fix '97-hid2hci.rules'.

* gnu/packages/linux.scm (bluez)[arguments]: Add 'post-install' phase.

gnu: bluez: Update to 5.40.

* gnu/packages/linux.scm (bluez): Update to 5.40.

gnu: bluez: Set sysconfdir and localstatedir.

* gnu/packages/linux.scm (bluez)[arguments]: Add '--sysconfdir=/etc'
and '--localstatedir=/var'.

gnu: services: Add bluetooth-service.

* gnu/services/desktop.scm (bluetooth-shepherd-service)
(bluetooth-service): New Prodecures.
(bluetooth-service-type): New variable.
* doc/guix.text (Desktop Services): Document it.

gnu: Add python2-jsonrpclib

* gnu/packages/python.scm (python2-jsonrpclib): New variable.

Signed-off-by: Leo Famulari <leo@famulari.name>

gnu: Add emacs-company.

* gnu/packages/emacs.scm (emacs-company): New variable.

gnu: certbot, python-acme: Update to 0.8.1.

These packages should be updated together.

* gnu/packages/tls.scm (certbot): Update to 0.8.1.
(python-acme, python2-acme): Update to 0.8.1

gnu: aria2: Update to 1.24.0.

* gnu/packages/bittorrent.scm (aria2): Updat eto 1.24.0.

services: dicod: Add 'interfaces' configuration field.

This makes 'dicod' listen on 'localhost' by default, whereas it was
previously listening on all the interfaces, which is not a good default
security-wise.

* gnu/services/dict.scm (<dicod-configuration>)[interfaces]: New field.
(dicod-configuration-file)[database->text]: New procedure, with code
formerly in 'dicod-configuration->text'.
[dicod-configuration->text]: Rename to...
[configuration->text]: ... this.  Honor 'interfaces'.
* doc/guix.texi (Various Services): Document 'interfaces'.

gnu: libqtxdg: Move qtbase to propagated-inputs.

* gnu/packages/lxqt.scm (libqtxdg)[inputs]: Move qtbase ...
[propagated-inputs]: ... to here.

This is a follow-up to aa450b2bc41b0cedbebc4f8c0a51867a436cf02b.

gnu: enlightenment: Update to 0.20.9.

* gnu/packages/enlightenment.scm (enlightenment): Update to 0.20.9.
[home-page]: Use https.

gnu: python-efl: Rebuild generated C files.

* gnu/packages/enlightenment.scm (python-efl)[arguments]: Replace 'build
phase to set 'ENABLE_CYTHON=1'.
[native-inputs]: python-cython.