res_stasis: Expose event for call forwarding and follow forwarded channel.

This change adds an event for when an originated call is redirected to
another target. This event contains the original channel and the newly
created channel. If a stasis subscription exists on the original originated
channel for a stasis application then a new subscription will also be
created on the stasis application to the redirected channel. This allows
the application to follow the call path completely.

(closes issue ASTERISK-22719)
Reported by: Joshua Colp

Review: https://reviewboard.asterisk.org/r/3054/


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@403808 f38db490-d61c-443f-a65b-d21fe96a405b
res_pjsip: Apply outbound proxy to all SIP requests.

Objects which are involved in SIP request creation and sending
now allow an outbound proxy to be specified. For cases where
an endpoint is used the outbound proxy specified there will
be applied.

(closes issue ASTERISK-22673)
Reported by: Antti Yrjola

Review: https://reviewboard.asterisk.org/r/3022/


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@403811 f38db490-d61c-443f-a65b-d21fe96a405b