Add missing include statement for compatibility with libstdc++ 11.

Taken from upstream:

  https://github.com/llvm/llvm-project/commit/b498303066a63a203d24f739b2d2e0e56dca70d1

diff --git a/utils/benchmark/src/benchmark_register.h b/utils/benchmark/src/benchmark_register.h
--- a/utils/benchmark/src/benchmark_register.h
+++ b/utils/benchmark/src/benchmark_register.h
@@ -1,6 +1,7 @@
 #ifndef BENCHMARK_REGISTER_H
 #define BENCHMARK_REGISTER_H
 
+#include <limits>
 #include <vector>
 
 #include "check.h"
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<tr><td><span title='2020-01-17 14:22:07 +0100'>2020-01-17</span></td><td><a href='/guix/commit/gnu/packages.scm?id=886a76073e4654449f413831897ffde736a07c91'>packages: Prevent inlining of 'find-best-packages-by-name'.</a><span class='msg-avail'>...<span class='msg-tooltip'>This allows 'tests/packages.scm' to mock it.

* gnu/packages.scm (find-best-packages-by-name): Set! it at the top
level to prevent it from being inline on Guile 3.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-01-06 16:31:54 +0100'>2020-01-06</span></td><td><a href='/guix/commit/gnu/packages.scm?id=6a7c4636d4dec47eefa03c95da5a1315bd0e0413'>Adjust module autoloads.</a><span class='msg-avail'>...<span class='msg-tooltip'>In Guile &lt; 2.9.7, autoloading a module would give you access to all its
bindings.  In future versions, autoloading a module gives access only to
the listed bindings, as per #:select (see &lt;https://bugs.gnu.org/38895&gt;).

This commit adjusts autoloads to the new semantics, allowing Guix to be
built with Guile 2.9.7/2.9.8.

* guix/build/download.scm &lt;top level&gt;: Remove call to 'module-autoload!'.
(load-gnutls): New procedure.
(tls-wrap): Call it.
* guix/git.scm &lt;top level&gt;: Remove call to 'module-autoload!'.
(load-git-submodules): New procedure.
(update-submodules): Call it instead of 'resolve-interface'.
* gnu/bootloader/grub.scm: Replace #:autoload with #:use-module.
* gnu/packages.scm: Likewise.
* gnu/packages/ssh.scm: Likewise.
* gnu/packages/tex.scm: Likewise.
* gnu/services/cuirass.scm: Likewise.
* gnu/services/mcron.scm: Likewise.
* guix/lint.scm: Augment list of bindings in #:autoload.
* guix/scripts/build.scm: Likewise.
* guix/scripts/gc.scm: Likewise.
* guix/scripts/pack.scm: Likewise.
* guix/scripts/publish.scm: Likewise.
* guix/scripts/pull.scm: Likewise.
* guix/utils.scm: Remove unnecessary #:autoload clauses; replace one
of them with #:use-module.
</span></span></td><td>Ludovic Courtès</td></tr>