__syncmessagesto_flags: store keywords
__syncmessagesto_flags: store keywords

This uses the destination folder's keyword mapping to translate the
message's keywords into some appropriate format.

Tested only with local Maildir.

Signed-off-by: Igor Almeida <8e5fad282a2f1b870d073527a312bc8b92350f3c@gmail.com>
Signed-off-by: Nicolas Sebrecht <347709267ddd1958560c4c317ea3fd613f10a719@laposte.net>

frioux/offlineimap,frioux/offlineimap