gnu: texinfo@5: Fix FTBFS with Perl >= 5.28.

* gnu/packages/patches/texinfo-5-perl-compat.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/texinfo.scm (texinfo-5)[source](patches): New field.

gnu/local.mk

@@ -1158,6 +1158,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/teensy-loader-cli-help.patch		\
   %D%/packages/patches/teeworlds-use-latest-wavpack.patch	\
   %D%/packages/patches/texinfo-perl-compat.patch		\
+  %D%/packages/patches/texinfo-5-perl-compat.patch		\
   %D%/packages/patches/texi2html-document-encoding.patch	\
   %D%/packages/patches/texi2html-i18n.patch			\
   %D%/packages/patches/thefuck-test-environ.patch		\

gnu/packages/patches/texinfo-5-perl-compat.patch

@@ -0,0 +1,19 @@
+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->__(

gnu/packages/texinfo.scm

@@ -69,6 +69,7 @@ is on expressing the content semantically, avoiding physical markup commands.")
               (method url-fetch)
               (uri (string-append "mirror://gnu/texinfo/texinfo-"
                                   version ".tar.xz"))
+              (patches (search-patches "texinfo-5-perl-compat.patch"))
               (sha256
                (base32
                 "1njfwh2z34r2c4r0iqa7v24wmjzvsfyz4vplzry8ln3479lfywal"))))