Cleanup compiler warnings

[codebrainz]

Old notes obsolete.

Should be a clean patch now, rebased on main with networking changes.

[codebrainz]

Rebased on main branch that had multiple incompatible fixes of same warnings (from network changes), got rid of the whitespace-only changes, and squashed all of the individual commits into a single commit to fix the remaining warnings.

Tested with QEMU that only the expected (non-trivial) warning is still shown and that it builds and runs.