Bug - panic() in SMPP shutdown

Either one of the SMPP receive/transmitter threads may
not be started depending on configuration.

But both are referenced in shutdown;

    if (smpp->transmitter) >= 0) gwthread_wakeup(smpp->transmitter); 
    gwthread_wakeup(smpp->receiver); 

the default values for these variables is -1 and
gwthread_wakeup() panic()'s on a -1 argument.

Suggested patch;

    if (smpp->transmitter >= 0) gwthread_wakeup(smpp->transmitter); 
    if (smpp->receiver>= 0) gwthread_wakeup(smpp->receiver); 

Paul Keogh
ANAM Wireless Internet Solutions
http://www.anam.com                     
+353 1 284 7555 (wired)               +353 86 234 6047 (wireless)
Castle Yard, Saint Patrick's Road, Dalkey, County Dublin, Ireland