imap: Removed now-unused cmd_sync_callback(), which doesn't work very well. See commit message in b7b25e0 for more details.

Avoid using (void)s by adding ATTR_NOWARN_UNUSED_RESULT attributes and other ways.

IMAP: Don't crash if IDLE command is pipelined after a long-running UID FETCH or UID SEARCH. --HG-- branch : HEAD

QRESYNC: Send HIGHESTMODSEQ automatically in all tagged replies whenever it seems useful. --HG-- branch : HEAD

Syncing supports now calling a callback after sync instead of just sending a tagged reply. Use it with EXPUNGE to retry EXPUNGE in case the syncing had seen new \Deleted flags (Outlook workaround). --HG-- branch : HEAD

When pipelining commands, delay synchronizations so that only one combined sync is performed for all the commands. This improves performance as well as fixes some problems with the earlier method. --HG-- branch : HEAD

Use mailbox_sync() instead of our own implementation. --HG-- branch : HEAD

Make sure we do a mailbox sync after flag updates (STORE, FETCH). Also added a new IMAP_SYNC_FLAG_SAFE which is used to figure out if appends and expunges are safe to send to client when delay-newmail workaround is enabled. --HG-- branch : HEAD

Changed .h ifdef/defines to use <NAME>_H format. --HG-- branch : HEAD

Added "bool" type and changed all ints that were used as booleans to bool. --HG-- branch : HEAD

UID STORE command must return UID parameter in FETCH replies. --HG-- branch : HEAD

Moved command-specific variables from struct client to struct client_command_context and changed code to use it. --HG-- branch : HEAD

Syncing works now too without buffering everything. Also fixed handling input while command was being processed. --HG-- branch : HEAD

Broke mailbox_sync() into iterator. --HG-- branch : HEAD