- cpu_set_kpc() now takes void *arg third argument, passed to the
entry point.
- cpu_fork() allows parent to be non-curproc iff parent is proc0.
When forking non-curproc, assume its state has already been saved.
- Adjust various pieces of machine-dependent code to account of all of this.
as this breaks C++ code that happens to indirectly include this header.
Both Matthias Scheler and I noticed this, independently.
This problem notably does not affect the atari and sun3/sun3x ports,
which have already implemented a similar solution.
