Versus from synchronous function calls, which doesn't work well because
the function call can see a script-layer state that doesn't reflect
the state as it will be in terms of the event/network stream.
A retry happens on every new input and also periodically based on a
timer. If a file handle is returned at those times, the input is
forwarded for analysis, else it keeps retrying until a timeout
threshold.
The framework now cycles through callbacks based on a table indexed
by analyzer tags, or the special case of service strings if a given
analyzer is overloaded for multiple protocols (FTP/IRC data). This
lets each protocol script bundle implement the callback locally and
reduces the FAF's external dependencies.
