overrides asyncore.dispatcher.handle_expt to do nothing, since
select.poll gives a POLLHUP error at the completion of these tests.
Added timeout & count arguments to several asyncore.loop calls to
avoid the possibility of a test hanging up a build. [GSoC - Alan
McIntyre]
find_prefix_at_end function. Check behavior of a string given as a
producer. Added tests for behavior of asynchat.async_chat when given
int, long, and None terminator arguments. Added usepoll attribute to
TestAsynchat to allow running the asynchat tests with poll support
chosen whether it's available or not (improves coverage of asyncore
code). [GSoC - Alan McIntyre]