This allows us to hook into the std libs implementation of parsing related stuff.
For this, we need to get rid of the distinction between a mailbox and a host
to just a single "address" field.
However this is already the common case. All but one users immediately
concatenated the mbox/domain to a single address.
So this in effects makes it simpler for most cases and we simply do the
transformation in the special case.
There was an unused error value as well as unnecessary usage of the sort
interface. There should now be less copying so a bit better performance
in some cases.
There is a command and config option. The criteria are a list of the
sort criterion and each can be individually reversed.
This only includes support for sorting in the maildir backend currently.
The other backends are not supported in this patch.
