util/find-doc-nits: Better parsing of links

When checking links, we need to peal away stuff that aren't part of
the link proper first.  That makes it easier to check the link
itself.
Reviewed-by: NPaul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/10507)

util/find-doc-nits

@@ -450,12 +450,14 @@ sub check {
     # Make sure every link has a section.
     while ( $contents =~ /$markup_re/msg ) {
         my $target = $1;
-        next unless $target =~ /^L</;           # Skip if not L<...>, or
+        next unless $target =~ /^L<(.*)>$/;     # Skip if not L<...>
+        $target = $1;                           # Peal away L< and >
+        $target =~ s/\/[^\/]*$//;               # Peal away possible anchor
+        $target =~ s/.*\|//g;                   # Peal away possible link text
+        next if $target eq '';                  # Skip if links within page, or
         next if $target =~ /::/;                #   links to a Perl module, or
-        next if $target =~ m@L</@;              #   links within the page, or
-        next if $target =~ /^L<https?:/;        #   is a URL link, or
-        next if $target =~ m@\([1357]\)>$@;     #   it has a section, or
-        next if $target =~ m@\([1357]\)/.*>$@;  #   it has a section/anchor
+        next if $target =~ /^https?:/;          #   is a URL link, or
+        next if $target =~ /\([1357]\)$/;       #   it has a section
         err($id, "Section missing in $target")
     }
     # Check for proper links to commands.