scantree.pl: indent pod template fragments (#482)

Pod in a heredoc is still treated as Pod by a pod viewer. This confuses
any tool trying to look for all Pod files.

Indenting the Pod fragments means they won't be interpreted as Pod, and
this indentation can be stripped off when writing the files.

Doc/scantree.pl

@@ -44,20 +44,24 @@
 $outindex="$outdir/Index.pod" unless (defined $outindex);
 unlink $outindex if -e $outindex;  # Handle read only file
 open my $podfh, ">", $outindex or die "couldn't open $outindex: $!";
-print $podfh <<'EOPOD';
+my $pod;
 
-=head1 NAME
+$pod = <<'EOPOD';
 
-PDL::Index - an index of PDL documentation
+  =head1 NAME
 
-=head1 DESCRIPTION
+  PDL::Index - an index of PDL documentation
 
-A meta document listing the documented PDL modules and
-the PDL manual documents
+  =head1 DESCRIPTION
 
-=head1 PDL manuals
+  A meta document listing the documented PDL modules and
+  the PDL manual documents
+
+  =head1 PDL manuals
 
 EOPOD
+$pod =~ s/^  //gm;
+print $podfh $pod;
 
 print $podfh "=over 4\n\n";
 for (@mans) {
@@ -66,13 +70,15 @@ =head1 PDL manuals
   print $podfh "=item *\n\n$ref\n\n";
 }
 
-print $podfh <<'EOPOD';
+$pod = <<'EOPOD';
 
-=back
+  =back
 
-=head1 PDL scripts
+  =head1 PDL scripts
 
 EOPOD
+$pod =~ s/^  //gm;
+print $podfh $pod;
 
 print $podfh "=over 4\n\n";
 for (@scripts) {
@@ -81,13 +87,15 @@ =head1 PDL scripts
   print $podfh "=item *\n\n$ref\n\n";
 }
 
-print $podfh <<'EOPOD';
+$pod = <<'EOPOD';
 
-=back
+  =back
 
-=head1 PDL modules
+  =head1 PDL modules
 
 EOPOD
+$pod =~ s/^  //gm;
+print $podfh $pod;
 
 print $podfh "=over 4\n\n";
 for (@mods) {
@@ -102,15 +110,17 @@ =head1 PDL modules
   print $podfh "=item *\n\n$ref\n\n";
 }
 
-print $podfh <<"EOPOD";
+$pod = <<'EOPOD';
 
-=back
+  =back
 
-=head1 HISTORY
+  =head1 HISTORY
 
-Automatically generated by scantree.pl for PDL version $PDL::VERSION.
+  Automatically generated by scantree.pl for PDL version $PDL::VERSION.
 
 EOPOD
+$pod =~ s/^  //gm;
+print $podfh $pod;
 
 close $podfh;