[PATCH] doc: acknowledge the MMDF mailbox format

[Eric Wong <e@80x24.org>]

While I don't currently see a point in supporting MMDF, we'll
still acknowledge it since mutt actually supports it.  Expand a
bit on MH while we're at it, since MH seems at least relevant.
---
 Documentation/lei-mail-formats.pod | 8 +++++++-
 Documentation/txt2pre              | 1 +
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/Documentation/lei-mail-formats.pod b/Documentation/lei-mail-formats.pod
index 8accedb4..da723d2b 100644
--- a/Documentation/lei-mail-formats.pod
+++ b/Documentation/lei-mail-formats.pod
@@ -82,7 +82,13 @@ mbox.
 =head1 MH
 
 Not yet supported, locking semantics (or lack thereof) appear to
-make it unsuitable for parallel access.
+make it unsuitable for parallel access.  It is widely-supported
+by a variety of MUAs and mailing list managers, however.
+
+=head1 MMDF
+
+Not yet supported, and it's unclear if current usage/support makes
+it worth supporting.
 
 =head1 IMAP
 
diff --git a/Documentation/txt2pre b/Documentation/txt2pre
index d98dfdd3..6367374d 100755
--- a/Documentation/txt2pre
+++ b/Documentation/txt2pre
@@ -117,6 +117,7 @@ $xurls{'ssoma(1)'} = 'https://ssoma.public-inbox.org/ssoma.txt';
 $xurls{'cgitrc(5)'} = 'https://git.zx2c4.com/cgit/tree/cgitrc.5.txt';
 $xurls{'prove(1)'} = 'https://perldoc.perl.org/prove.html';
 $xurls{'mbox(5)'} = 'https://manpages.debian.org/stable/mutt/mbox.5.en.html';
+$xurls{'mmdf(5)'} = 'https://manpages.debian.org/stable/mutt/mmdf.5.en.html';
 
 my $str = do { local $/; <STDIN> };
 my ($title) = ($str =~ /\A([^\n]+)/);