The three classes with names starting with UsefulIMAP4 were used for two
purposes, to include the UsefulIMAPMixIn class and to implement various
system-specific kludges. None of these kludges remain, so it is cleaner
to include UsefulIMAPMixIn directly in imaplibutil and forget about them
for good.
Signed-off-by: Vincent Beffara <vbeffara@ens-lyon.fr>
Reviewed-by: Sebastian Spaeth <Sebastian@SSpaeth.de>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>