Initial support for more current Raspberry Pi models (i.e. 5) (#65)

* start work, based on https://github.com/AndrewFromMelbourne/raspberry_pi_revision/blob/master/raspberry_pi_revision.c

* this isn't right yet, need to find datasheets, and this switch needs a lot more cases

* docmument research

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Co-authored-by: Bluefooted Boobie <scot@birdhouse>

fs,sysfs: use EPOLL_EXEC to clean up epoll file descriptors on execve…

…(2) (#32)

EPOLL_EXEC is O_CLOEXEC for epoll_create1, which is a good default for
any file descriptor not explicitly designed to survive an exec.

Bump to go1.20 (#33)

Run go mod tidy

Update to go1.17

Update deprecated code.
Update github actions.
Update dependencies.

github actions: improve actions for go1.17

host: remove ftdi (again)

It's not yet stable enough. Will continue iterating on it.

Bump conn/v3 from v3.6.7 to v3.6.8

No significant change.

Create a formal broken v0

This is to save user from confusion with different version.
It seeds pkg.go.dev with a formal page to redirect them to the right version.

go.mod: update for v3.6.7