#41 usb.h is actually USB.h (case sensitive Macintosh file system)

[JD Klein]

In src/native/usb/osx/NativeUSBMacOSX.c, I had to change usb.h to USB.h on a case sensitive Mac file system to get it to compile on Mojave.

This will not affect most Macs because they default to case insensitive, but should probably be fixed because case sensitive is a valid file system choice.