Fix: setting default externip to 0.0.0.0, to make the ipaddress parser happy. Reenabled showing externip in cli:'sccp show globals'. Use anyaddress check in sccp_socket_getExternalAddr() to see if default value has been replaced by an actual address. (Re-Reported by Pavel)

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@5617 43c1dc8c-776e-4df2-8ef1-6e829299be21