podwrapper: simplify external references pointing to self

When convering a POD documentation, possibily combining various
sub-documents together, simplify the L<> links that explicitly point to
the very same documentation being generated.

For example, when generating the virt-builder documentation, links like
  L<virt-builder(1)/SECTION>
will be turned into
  L</SECTION>
thus not making Pod::Simple parse them as external reference.

While it is a slightly crude hack, it seems there's no easy way to
process the link parsing with Pod::Simple subclasses.

podwrapper.pl.in

@@ -278,6 +278,9 @@ foreach (@inserts) {
         if $content eq $oldcontent;
 }
 
+# Turn external links to this man page into simple cross-section links.
+$content =~ s,\QL<$name($section)/\E,L</,g;
+
 # Perform @verbatims.
 foreach (@verbatims) {
     my @a = split /:/, $_, 2;