Today, aliases parsing is too lax, silently ignoring most kinds of invalid
lines.
That behaviour can cause a lot of confusion when users think the aliases
are being parsed, and also cause problems when extending the syntax.
This patch fixes that problem by making aliases parsing return errors on
the invalid lines.
Unfortunately this will cause some previously-accepted files to now be
rejected, but it should be quite visible.
This patch implements support for catch-all aliases, where users can add
a `*: destination` alias. Mails sent to unknown users (or other aliases)
will not be rejected, but sent to the indicated destination instead.
Please see https://github.com/albertito/chasquid/issues/23 and
https://github.com/albertito/chasquid/pull/24 for more discussion and
background.
Thanks to Alex Ellwein (aellwein@github) for the alternative patch and
help with testing; and to ThinkChaos (ThinkChaos@github) for help with
testing.
