main/cdrs: Preserve context/extension when executing a Macro or GoSub

The context/extension in a CDR is generally considered the destination of a
call. When looking at a 2-party call CDR, users will typically be presented
with the following:

context    exten      channel     dest_channel app  data
default    1000       SIP/8675309 SIP/1000     Dial SIP/1000,,20

However, if the Dial actually takes place in a Macro, the current behaviour
in 12 will result in the following CDR:

context    exten      channel     dest_channel app  data
macro-dial s          SIP/8675309 SIP/1000     Dial SIP/1000,,20

The same is true of a GoSub:

context    exten      channel     dest_channel app  data
subs       dial_stuff SIP/8675309 SIP/1000     Dial SIP/1000,,20

This generally makes the context/exten fields less than useful.

It isn't hard to preserve these values in the CDR state machine; however, we
need to have something that informs us when a channel is executing a
subroutine. Prior to this patch, there isn't anything that does this.

This patch solves this problem by adding a new channel flag,
AST_FLAG_SUBROUTINE_EXEC. This flag is set on a channel when it executes a
Macro or a GoSub. The CDR engine looks for this value when updating a Party A
snapshot; if the flag is present, we don't override the context/exten on the
main CDR object. In a funny quirk, executing a hangup handler must *not* abide
by this logic, as the endbeforehexten logic assumes that the user wants to see
data that occurs in hangup logic, which includes those subroutines. Since
those execute outside of a typical Dial operation (and will typically have
their own dedicated CDR anyway), this is unlikely to cause any heartburn.

Review: https://reviewboard.asterisk.org/r/3962/

ASTERISK-24254 #close
Reported by: tm1000, Tony Lewis
Tested by: Tony Lewis
........

Merged revisions 422718 from http://svn.asterisk.org/svn/asterisk/branches/12
........

Merged revisions 422719 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@422720 65c4cc65-6c06-0410-ace0-fbb531ad65f3