lowl-vcom: Added support for auto scanning (-S auto) on Mac OS X
Uses I/O Kit to enumerate USB devices
https://developer.apple.com/library/mac/documentation/DeviceDrivers/Conceptual/IOKitFundamentals/Introduction/Introduction.html
http://en.wikipedia.org/wiki/I/O_Kit
Merge pull request #489 from nwoolls/feature/scan-support-osx

lowl-vcom: Add support for auto scanning (-S auto) on Mac OS X