Make PTP DivertingLegInformation3 message behavior closer to the specifications.

Make PTP DivertingLegInformation3 message behavior closer to the specifications.

*  Wait for a DivertingLegInformation3 message after receiving a
DivertingLegInformation1 message to complete the redirecting-to information
before queuing a redirecting update to the other channel.

*  A DivertingLegInformation2 message should be responded to with a
DivertingLegInformation3 when the COLR is determined.  If the call
could or does experience another redirection, you should manually
determine the COLR to send to the switch by setting REDIRECTING(to-pres)
to the COLR and setting REDIRECTING(to-num) = ${EXTEN}.

*  A DivertingLegInformation2 message must have an original called number
if the redirection count is greater than one.  Since Asterisk does
not keep track of this information, we can only indicate that the
number is not available due to interworking.

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@190735 65c4cc65-6c06-0410-ace0-fbb531ad65f3