system_id is a char array, which makes the NULL check a tautology,
so we should check with strlen if the string is empty or not.
This is fixing the "write" command of VTY that would otherwise
create a config file that can not be parsed.
If an ESME has the dcs_transparent config flag, then the TP-DCS
of MO-SMS is transparently passed to SMPP and not converted to SMPP
specific data_coding values.
This is needed in cases where ESMEs actually care about the exact
TP-DCS, as the conversion from TP-DCS to SMPP data_coding is not
bijective.
An ESME can now be configured in the VTY to enable osmocom-extensions,
which will add vendor-specific SMPP TLVs for RxLev/RxQual/ARFCN/IMEI and
transmit power to the SMPP DELIVER-SM message type.
Holger Hans Peter Freyther
Harald Welte