This is an import of https://github.com/Yubico/libfido2 1.8.0 (20210722)

Local changes:

Only a subset of the upstream files have been imported: src/, man/ and LICENSE.

The CMake-based build system has been replaced with a fixed Makefile.

src/hid_openbsd.c has been adapted to use the fido(4) device.
src/random.c has had CSPRNG interfaces other than arc4random_buf(4) removed