FreeBSD hidraw backend to replace libusb backend

[mcuee]

• HID reports of more than 64 bytes and libusb backend #274 (comment)

It would be good we have a FreeBSD specific backend using hidraw for HIDAPI so that FreeBSD HIDAPI users no longer need to use the libusb backend.

Reference:
https://reviews.freebsd.org/D27992

This driver provides raw access to HID devices through uhid(4)-compatible interface and is based on pre-8.x uhid(4) code.

Unlike uhid(4) it does not take devices in to monopoly ownership and allows parallel access from other drivers.
hidraw supports Linux's hidraw-compatible interface as well.

[mcuee]

From @wulf7

• HID reports of more than 64 bytes and libusb backend #274 (comment)

I already added hidraw enumeration support to https://github.com/wulf7/libudev-devd/
So, most probably, addition of linux hidapi backend to build is only thing left.

[mcuee]

@wulf7

Please help to review the current hidraw backend for Linux and see what would be needed to change to make it working under FreeBSD hidraw. PR will be more than welcome.

• https://github.com/libusb/hidapi/blob/master/linux/hid.c

[mcuee]

Hopefully #730 will be able to address this issue.

• Add hidraw backend for FreeBSD #730