(closes issue #10668)

(closes issue #10668)
(closes issue #11721)
(closes issue #12726)
Reported by: arkadia
Tested by: murf

These changes:

1. revert the changes made via bug 10668;
   I should have known that such changes,
   even tho they made sense at the time,
   seemed like an omission, etc, were actually
   integral to the CDR system via forkCDR.
   It makes sense to me now that forkCDR didn't
   natively end any CDR's, but rather depended
   on natively closing them all at hangup time
   via traversing and closing them all, whether
   locked or not. I still don't completely
   understand the benefits of setvar and answer
   operating on locked cdrs, but I've seen
   enough to revert those changes also, and
   stop messing up users who depended on that
   behavior. bug 12726 found reverting the changes
   fixed his changes, and after a long review
   and working on forkCDR, I can see why.
2. Apply the suggested enhancements proposed
   in 10668, but in a completely compatible
   way. ForkCDR will behave exactly as before,
   but now has new options that will allow some
   actions to be taken that will slightly
   modify the outcome and side-effects of
   forkCDR. Based on conversations I've had
   with various people, these small tweaks
   will allow some users to get the behavior
   they need. For instance, users executing
   forkCDR in an AGI script will find the
   answer time set, and DISPOSITION set,
   a situation not covered when the routines
  were first written.
3. A small problem in the cdr serializer
   would output answer and end times even
   when they were not set. This is now
   fixed.

git-svn-id: http://svn.digium.com/svn/asterisk/branches/1.4@118858 614ede4d-c843-0410-af14-a771ab80d22e