Increase SKINNY_MAX_PACKET and add some logging.

Increase SKINNY_MAX_PACKET to 2000 bytes to handle some messages
in v17 that are greater than the old 1000 bytes. Also add some
useful logging regarding packet and session handling.

A device (with protocol v17) was sending a packet with length 
greater than 1000 which resulted in the TCP session being
destroyed and registration being retryed.



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@340070 65c4cc65-6c06-0410-ace0-fbb531ad65f3