implement flushEvents() flushDigits() setAutoHangup() and setHangupHook().  reworked dtmfhandler and some aspects relating to threadstate.  folded in memory pool thing from mishehu.  added more asserts to switch_core_file (coordinated w/ anthony on this)

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@5442 d0543943-73ff-0310-b7d9-9358b9ac24b2