this prepares the code for being called from a callback.
notably, this makes the imap list parser have a "soft stack", so the
recursion can be suspended at any time.
synchronous error codes which are passed through callbacks aren't a
particularly good idea, after all: latest when the callback does stuff
which does not concern the caller, the return code becomes ambiguous.
instead, protect the sync_vars object with a refcount when invoking
driver functions from loops, as the callbacks they call could invalidate
the object and we would have no way of knowing that the loop should be
aborted prematurely. the upcoming async imap driver will also need a
refcount to protect the cancelation marker of the imap socket dispatcher
loop.
that way we don't have to piggy-back (possibly asynchronous) fatal
errors to particular commands.
internally, the drivers still use synchronous return values as well,
so they don't try to access the invalidated store after calling back.
imap may very well store messages with LF line endings. only RFC2822
requires CRLF.
consequently, preserve the line endings as much as possible unless the
mailbox format does not support it (this would be the case for unix mbox
- i actually have no idea about maildir).
- wrap message (un)expirations into transactions
- no redundand flag propagations in conjunction with expirations
- better prepared for the upcoming async operation
as opposed to earlier threats, BerkDB was not entirely dropped; i
suppose the isync 0.7 -> 0.8 change had a reason, so i added an
alternative UID storage scheme.
note that BDB 4.0 is not sufficient, as the db->open function changed in
an incompatible way ...
i updated the debian packaging except for a changelog entry.
note that i removed the upgrade blurb, as upstream now has a smooth
upgrade path down to at least isync 0.4.
unneeded (i.e., if MaxSize is not specified in the config file).
Patch and idea originally from Nicolas Boullis <nboullis@debian.org>,
modified/polished by Theodore Ts'o per comments by Oswald Buddenhagen.
