res/res_pjsip_dlg_options: Add a module to handle in-dialog OPTIONS requests

This patch adds a new session supplement that handles in-dialog OPTIONS
requests. Said OPTIONS requests are sent a 200 OK, as an endpoint lookup
for the OPTIONS request would already have been done by the time the
session supplement receives the inbound request.

ASTERISK-24862 #close
Reported by: yaron nahum
patches:
  res_pjsip_dlg_options.c submitted by yaron nahum (License 6676)


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/13@434506 65c4cc65-6c06-0410-ace0-fbb531ad65f3