Fix for <https://nvd.nist.gov/vuln/detail?vulnId=CVE-2015-8327>.

--- a/util.c	2014-06-20 19:26:18 +0000
+++ b/util.c	2015-10-30 15:45:03 +0000
@@ -31,7 +31,7 @@
 #include <assert.h>
 
 
-const char* shellescapes = "|<>&!$\'\"#*?()[]{}";
+const char* shellescapes = "|<>&!$\'\"`#*?()[]{}";
 
 const char * temp_dir()
 {

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<div class='path'>path: <a href='/guix/log/?id=ee711c7c2136dadcae1315bc7e93b3f28bc507f4'>root</a>/<a href='/guix/log/gnu.scm?id=ee711c7c2136dadcae1315bc7e93b3f28bc507f4'>gnu.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu.scm?id=ee711c7c2136dadcae1315bc7e93b3f28bc507f4&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2019-03-24 23:06:11 +0100'>2019-03-24</span></td><td><a href='/guix/commit/gnu.scm?id=db1e2522f6222594fc507ce7a7ba7b1c0ac5037d'>Add (gnu system keyboard).</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/system/keyboard.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.
* gnu.scm (%public-modules): Add it.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2017-11-08 22:36:20 +0100'>2017-11-08</span></td><td><a href='/guix/commit/gnu.scm?id=c5a4a92f1a796e342b7db4c458f1fdb61ffc8d40'>gnu: Improve error reporting of the use-.*modules macros.</a><span class='msg-avail'>...<span class='msg-tooltip'>Suggested by Julien Lepiller and myglc2
at &lt;https://lists.gnu.org/archive/html/guix-devel/2017-11/msg00106.html&gt;.

* gnu.scm (%try-use-modules): New procedure.
(package-module-hint, service-module-hint): New procedures.
(try-use-modules): New macro.
(use-package-modules, use-service-modules, use-system-modules): Use it.
* tests/guix-system.sh: Test it.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2017-05-16 14:41:01 +0200'>2017-05-16</span></td><td><a href='/guix/commit/gnu.scm?id=b09a8da4a2e50845a297e041762f3ff9e649c047'>bootloader: Add extlinux support.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/bootloader.scm: New file.
* gnu/bootloader/extlinux.scm: New file.
* gnu/bootloader/grub.scm: New file.
* gnu/local.mk: Build new files.
* gnu/system.scm: Adapt to new bootloader api.
* gnu/scripts/system.scm: Adapt to new bootloader api.
* gnu.scm: Remove (gnu system grub) and replace by (gnu bootloader) and (gnu
bootloader grub) modules.
* gnu/system/grub.scm: Moved content to gnu/bootloader/grub.scm.
* gnu/system/vm: Replace (gnu system grub) module by (gnu bootloader).
* gnu/tests.scm: Ditto.
* gnu/tests/nfs.scm: Ditto.
</span></span></td><td>Mathieu Othacehe</td></tr>