febe interface async?

[Paul Baclaski <autodesk!thezahir!peb>]

We need to know whether the febe interface (and obviously, fm) is
reentrant and asynchronous.  This affects the design of the montage
scheduler and also impacts the user interface.   

Although the server can process only one request at a time, it would be
nice if the user could click-ahead such that there is some window
feedback and the display is fully changed when the backend processes
the requests.  Furthermore, while the backend is processing a request,
montage should not block so that scheme engines can continue to work.

This also brings up the question:  what is the protocol for sensor
events?  There are even more reasons why this should be asynchronous.

(Note that the tcp/ip interface is not reentrant and asynchronous, so
the real question is the net interface wrapped so as to appear
asynchronous--uses non-blocking select() and a timer, etc.)


Paul