working libgpiod_pulsein on pi: add sysv_ipc dep; add pulseio to py_modules

The included libgpiod_pulsein binary wasn't being used on the Pi,
specifically with Adafruit_CircuitPython_DHT.  It turns out that
`pulseio` was missing from the list of modules to install, we weren't
installing `sysv_ipc` as a dependency, and `libgpiod_pulsein` itself
wasn't marked as executable.

This is now tested and working on a Pi 3B+ with a DHT22.