Obey device->dtmmode setting when creating a new channel, Use dtmfmode when sending digits, inband or outofband. Updated sccp_protocol.c to set the correct dtmfmode.

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@5454 43c1dc8c-776e-4df2-8ef1-6e829299be21