Automatically re-synchronize the IMAP protocol. Previously, losses of

synchronization could happen if an Exception was thrown while parsing
an untagged response without using executeSimpleCommand.  For
instance, while doing a fetch.  Once synchronization was lost, later
commands would fail in surprising ways.  One manifestation of such
failures was spontaneously emptying of folders when search results
were not returned properly.  The new code makes sure to only accept OK
responses with the tag of the command, and discards the untagged
responses from previous command.