main/astobj2: Make REF_DEBUG a menuselect item; improve REF_DEBUG output

This patch does the following:
(1) It makes REF_DEBUG a meneselect item. Enabling REF_DEBUG now enables
    REF_DEBUG globally throughout Asterisk.
(2) The ref debug log file is now created in the AST_LOG_DIR directory.
    Every run will now blow away the previous run (as large ref files
    sometimes caused issues). We now also no longer open/close the file
    on each write, instead relying on fflush to make sure data gets written
    to the file (in case the ao2 call being performed is about to cause a
    crash)
(3) It goes with a comma delineated format for the ref debug file. This
    makes parsing much easier. This also now includes the thread ID of the
    thread that caused ref change.
(4) A new python script instead for refcounting has been added in the
    contrib/scripts folder.

Review: https://reviewboard.asterisk.org/r/3377/

git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/1.8@412114 f38db490-d61c-443f-a65b-d21fe96a405b