That's got to be one of the hardest macro names to read, ever,
(it's phrased with an implicit negative in the condition,
rather than something simple like "assert").
Plus, it's evil, since it's a macro with a return in it.
And finally, it's actually *longer* than just typing "if"
and "return". So what's the point of this ugly idiom?
We can't rely on any gmime-internal headers, (and fortunately we
don't need to). We also aren't burdened with any autconf machinery
so don't reference any of that.
We're sucking in one gmime implementation file just to get the
piece that parses an RFC 822 date, because I don't want to go
through the pain of replicating that.
