DaqDeviceIndex/OSX: Make sure selected daq has nroutputs > 0.

Not that it helped. DaqAInScan fails just as miserably on OSX 10.9 as
it did on 10.7 and 10.5. Seems that one 10.8 machine of user masondar
is the only one that actually works with 64-Bit PTB. Oh, and 10.9
scrambles ordering of daq interfaces even worse than 10.7 did. Strong
work Apple!