add send_info dp app and uuid_send_info FSAPI and execute_on_sip_extra_headers and api_on_sip_extra_headers handler variables

comment out optional Require header from re-invites for the sake of interop with testy t.38 terminals

FS-3714 --resolve You are using the sip_from_host and sip_to_host which are calculated based on the response from the other end, this patch will pre-populate the variables with what it is suspeceted to be in these values but they are not guranteed to be right if there was forwarding etc and also it will not always be an ip if you send to foo@domain.com the sip_to_host will be domain.com until it replies.  This is the best you will get....

FS-3686 --resolve no wonder I am so baffled one of the files did not save into git when I did the patch

No more "invalid span", now it's either "'foo' not a libpri span" or
"'foo' span not found" which makes it a lot more useful.
Signed-off-by: Stefan Knoblich <stkn@openisdn.net>

Signed-off-by: Stefan Knoblich <stkn@openisdn.net>