TODO
Fix regression in sending the incorrect status code.
Only keep the map entries for one sync cycle, not 2.
Add Horde_ActiveSync_Imap_Message::getFlags()
Pass through for FILTERTYPE_INCOMPLETETASKS.

Not used yet in the driver, but we shouldn't drop the value.
Initial library support for sending custom imap flags as EAS message categories.
Backend support for sending/receiving EAS mail category changes.
phpdoc
Next attempt at Bug: 13405
Update custom flags, if able to.
Add IMP_Api::addFlags()

Allow for adding/ensuring a set of custom msgflags are added to prefs.
Typo in phpdoc.