tests: Fix list of exports in (gnu tests).

* gnu/tests.scm: Export 'marionette-service-type'.

tests: Export 'run-basic-test'.

* gnu/tests/base.scm (run-basic-test): New procedure, extracted from ...
(%test-basic-os): ... here.  Use it.

tests: Strengthen regexp in 'packages.scm'.

* tests/packages.scm ("--search-paths with pattern"): Call
'regexp-quote' on the result of 'derivation->output-path'.

gnu: guix: Add 'current-guix' thunk.

* gnu/packages/package-management.scm (source-file?)
(make-git-predicate, current-guix): New procedures.

utils: 'current-source-directory' gracefully handles lack of source info.

* guix/utils.scm (current-source-directory): Add case for when FILE-NAME
is #f.

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