AT+CFUN=4 will be used when available to go to standby mode. If not supported,
(as in EGS5) AT+CFUN=7 will be used instead, which enables a CYCLIC SLEEP mode.
Flow control setup was updated to RCS/CTS so that waking up from sleep mode
works properly.
We try to look for 'psinfo' indication in AT^SIND? output (available in 3G
devices from Cinterion), and if that is not available, we try to use the
AT^SMONG GPRS monitor (available in 2G devices from Cinterion).