Change to docs reporting form

Greetings,

In order to avoid having emails generated from the doc reporting form be
considered as spam by lots of people because it's clearly forged email,
we've changed the 'From' to be a 'noreply' address and set the
'Reply-To' to be the original sender and the mailing list.

Hopefully this change will have little impact on the users of this
mailing list while reducing the amount of our outbound email that gets
blocked for being spam/forged (and, therefore, also decreases the load
on our moderators and makes our systems less likely to be considered
spam sources by the big email providers).

If you have any issues, please let me know, or post your concern to
pgsql-www.

Thanks!

Stephen