Fix a deprecation warning with newer Perl that breaks some tests.

--- a/tp/Texinfo/Parser.pm
+++ b/tp/Texinfo/Parser.pm
@@ -5438,12 +5438,12 @@
     }
   } elsif ($command eq 'clickstyle') {
     # REMACRO
-    if ($line =~ /^\s+@([[:alnum:]][[:alnum:]\-]*)({})?\s*/) {
+    if ($line =~ /^\s+@([[:alnum:]][[:alnum:]\-]*)(\{})?\s*/) {
       $args = ['@'.$1];
       $self->{'clickstyle'} = $1
         unless(_ignore_global_commands($self));
       $remaining = $line;
-      $remaining =~ s/^\s+@([[:alnum:]][[:alnum:]\-]*)({})?\s*(\@(c|comment)((\@|\s+).*)?)?//;
+      $remaining =~ s/^\s+@([[:alnum:]][[:alnum:]\-]*)(\{})?\s*(\@(c|comment)((\@|\s+).*)?)?//;
       $has_comment = 1 if (defined($4));
     } else {
       $self->line_error (sprintf($self->__(
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<tr><td><span title='2020-02-12 20:35:43 +0100'>2020-02-12</span></td><td><a href='/guix/commit/gnu/build/cross-toolchain.scm?id=89da127035737bdf922bc566970c5506c2e01b00'>gnu: cross-base: Switch back to 'CROSS_C_INCLUDE_PATH' &amp; co.</a><span class='msg-avail'>...<span class='msg-tooltip'>This is a followup to 2073b55e6b964cb8ca15e8c74cb32dac00f05f0d.

* gnu/build/cross-toolchain.scm (%gcc-include-paths): Switch back to
'C_INCLUDE_PATH' &amp; co.
* gnu/packages/cross-base.scm (%gcc-include-paths): Likewise.
(cross-gcc-arguments): Remove 'treat-glibc-as-system-header' phase.
(cross-gcc)[native-inputs]: Reorder so that libc comes last.
[search-paths]: Add "include/c++" for 'CROSS_CPLUS_INCLUDE_PATH'.
* guix/build-system/gnu.scm (standard-cross-packages): Have "cross-gcc"
appear both for 'host and 'target.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-08-29 17:19:18 -0400'>2019-08-29</span></td><td><a href='/guix/commit/gnu/build/cross-toolchain.scm?id=0481289cbccba2646bf654f0ae49ac9c45602d5d'>Merge branch 'master' into core-updates</a></td><td>Mark H Weaver</td></tr>
<tr><td><span title='2019-08-28 08:47:14 -0400'>2019-08-28</span></td><td><a href='/guix/commit/gnu/build/cross-toolchain.scm?id=07d7175406210434d1fb9c100dc33a7d095f1627'>gnu: mingw-w64: Update to 6.0.0.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/mingw.scm (mingw-w64): Update to 6.0.0.
* gnu/packages/patches/mingw-w64-6.0.0-gcc.patch: New file.
* gnu/packages/patches/mingw-w64-5.0rc2-gcc-4.9.3.patch: Delete it.
* gnu/local.mk (dist_patch_DATA): Add new patch.  Delete old patch.
* gnu/build/cross-toolchain.scm (set-cross-path/mingw): Add additional
  autoconf-like substitutions.
</span></span></td><td>David Thompson</td></tr>
<tr><td><span title='2019-08-22 15:53:27 -0400'>2019-08-22</span></td><td><a href='/guix/commit/gnu/build/cross-toolchain.scm?id=893c2df00daa4e6dd6a7ff3813d7df5329877f9e'>Merge branch 'master' into core-updates</a></td><td>Mark H Weaver</td></tr>
<tr><td><span title='2019-08-14 21:29:53 +0200'>2019-08-14</span></td><td><a href='/guix/commit/gnu/build/cross-toolchain.scm?id=67dac6b8920755cb011047157bb7b4fae4760143'>gnu: mingw: Add x86_64 support.</a><span class='msg-avail'>...<span class='msg-tooltip'>This patch parameterizes previously hard-coded instances of
i686-w64-mingw32, adding support for x86_64-w64-mingw32.

* gnu/packages/mingw.scm (make-mingw-w64): New procedure.
(mingw-w64-i686, mingw-w64-x86_64): New variables.
(%mingw-triplet): Remove.
(mingw-w64): Update to point to 'mingw-w64-i686'.
* gnu/packages/cross-base.scm (cross-gcc): Use 'libc' keyword argument
if specified, instead of treating it as a boolean.
(native-libc): Return the correct mingw-w64 depending on machine
specified in target.
* gnu/packages/bootstrap.scm (glibc-dynamic-linker): Add "x86_64-mingw".
* gnu/build/cross-toolchain.scm (set-cross-path/mingw): Replace
hardcoded 'i686-w64-mingw32' instances with 'target' keyword argument.
(cross-gcc-build-phases): Update accordingly; use 'target-mingw?'
implementation of target checking and add commentary.
* gnu/ci.scm (%cross-targets): Add "x86_64-w64-mingw32".
</span></span></td><td>Carl Dong</td></tr>