[antlr-interest] change to list text/html processing

[Terence Parr]

Hi, Graham W pointed out that "there has been a sharp increase in HTML-only emails this past year", which yield empty messages with links to an attachment.

I think we should auto convert those to text.  I.e., should Mailman convert text/html parts to plain text? This conversion happens after MIME attachments have been stripped.  I'll be turning on filtering and who knows what else this will mess up.  Anybody care if i try this feature out?

Ter