Additional documentation for bindaddr.

Note that bindaddr will only enable UDP instead of both UDP and TCP which is
what I would expect for backwards compatibility with systems being upgraded
which only support UDP transportation.

(closes issue ASTERISK-17976)
Reported by: Sean Darcy

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@323234 65c4cc65-6c06-0410-ace0-fbb531ad65f3

configs/sip.conf.sample

@@ -147,6 +147,10 @@ allowoverlap=no                 ; Disable overlap dialing support. (Default is y
 ; (Note that using bindaddr=:: will show only a single IPv6 socket in netstat.
 ;  IPv4 is supported at the same time using IPv4-mapped IPv6 addresses.)
 ;
+; Using bindaddr will only enable UDP support in order to be backwards compatible with those systems
+; that were upgraded prior to TCP support. Use udpbindaddr and tcpbindaddr to bind to UDP and TCP
+; independently.
+;
 ; You may optionally add a port number. (The default is port 5060 for UDP and TCP, 5061
 ; for TLS).
 ;   IPv4 example: bindaddr=0.0.0.0:5062