*) Rename *event_handler* to state_handler to avoid confusion with newer eventing engine.
*) Allow application level of state_handler to be layered/stacked (up to 30)
*) Add new core global state_handler stack (also up to 30.. seems reasonable, constant in switch_types.h)



git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@554 d0543943-73ff-0310-b7d9-9358b9ac24b2