Made inga_tool compiling under OS X

with this PR inga_tool gets more or less usable under OS X
(the problems with unloading drivers for specific usb-devices still remain and are not solveable due to [TN2315](https://developer.apple.com/library/mac/technotes/tn2315/_index.html#//apple_ref/doc/uid/DTS40014014-CH1-TNTAG3))