Add error reporting to the MacOS port.

[hardkrash]

Initial implementation of error messages for the macOS port.

Interface mostly copied from the linux port. Messages probably need some love for the other errors being reported.

[hardkrash]

This is to resolve issue #310

[Youw]

Hi @hardkrash,

Are you still up to finish this PR? I've started some changes for hidraw backend: https://github.com/libusb/hidapi/pull/428, those introduce a safe strategy for hid_error and allows to proceed with the implementation for other (this one) backends.

[mcuee]

#428 has been merged.

[Youw]

I guess if any objections/improvements - we'll be fixing them in master.