Addition of the FrameHook API (AKA AwesomeHooks)

Addition of the FrameHook API (AKA AwesomeHooks)

So far all our tools for viewing and manipulating media streams
within Asterisk have been entirely focused on audio.  That made
sense then, but is not scalable now.  The FrameHook API lets us
tap into and manipulate _ANY_ type of media or signaling passed
on a channel present today or in the future.  This tool is a step
in the direction of expanding Asterisk's boundaries and will help
generate some rather interesting applications in the future.

In addition to the FrameHook API, a simple dialplan function
exercising the api has been included as well.  This function
is called FRAME_TRACE().  FRAME_TRACE() allows for the internal
ast_frames read and written to a channel to be output.  Filters
can be placed on this function to debug only certain types of frames.
This function could be thought of as an internal way of doing
ast_frame packet captures.

Review: https://reviewboard.asterisk.org/r/925/

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@287647 65c4cc65-6c06-0410-ace0-fbb531ad65f3