Building libusb support on Windows and macOS

[slouken]

SDL has a change to allow building hidapi with libusb support on Windows. It was done by abstracting the threading interface, so it can be replaced by other implementations, and the pthread implementation is provided by default.

Please let me know if you'd like this change as a PR!
libsdl-org/SDL@57b33ae

[mcuee]

Yes please file a PR.

This will also (partially) address the following issue.

• libusb backend for Windows and macOS #319
• Add Windows quirks to documentation and potential Windows libusb backend #61

[mcuee]

@slouken

If possible, you may also want to add macOS support. macOS libusb support is not so useful for real application (requires sudo or some difficult-to-attain entitlement), but it may be useful to troubleshooting purpose and maybe useful for some devices.

[slouken]

The current code works on macOS without any changes. I tested with it a few days ago.