Brendan Cully's latest changes:

Brendan Cully's latest changes:

* includes all of my last patch, since it hasn't been committed yet.
* catches a couple segfault problems if Context is NULL.
* works harder to avoid sending null STORE FLAGS commands. May not
  be perfect yet, but also has extra debugging code.
* has the beginnings of a more interactive IMAP error handler.
  Doesn't do anything yet, I'm just including it because I want to
  get the rest of the patch out.