removed the ifdef JMZ stuff
use WANT_LATENCY_CALLBACK to enable latency-callbacks
added 'processing' kwd to __init__ to turn of process-callback

so instantiating
  j=jack.Client("foo", processing=False)
will create a client that doesn't register a processing callback...
auto-disable processing in case of errors

when we cannot create a socketpair, we might as well not do processing().
LATER: make this a bit more intelligent...
remove debugging output in dealloc()
no more source-code patching

simply define "JACK2=1" when calling the compiler, rather than patching the sourcecode