Include Expires header for SIP PUBLISH requests

RFC3903 requres SIP PUBLISH requests to have Expires headers, so add
them.

Review: https://reviewboard.asterisk.org/r/2003/
Patch-by: gareth
........

Merged revisions 370014 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10@370015 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -10566,7 +10566,7 @@ static int respprep(struct sip_request *resp, struct sip_pvt *p, const char *msg
 		add_header(resp, "Session-Expires", se_hdr);
 	}
 
-	if (msg[0] == '2' && (p->method == SIP_SUBSCRIBE || p->method == SIP_REGISTER)) {
+	if (msg[0] == '2' && (p->method == SIP_SUBSCRIBE || p->method == SIP_REGISTER || p->method == SIP_PUBLISH)) {
 		/* For registration responses, we also need expiry and
 		   contact info */
 		char tmp[256];