This does not buy us new functionnality for now, because we still have to
discover how mach_init (which acts as a name server, enabling processes to
discover each other's ports) is able to receive messages from other processes
(this is a bootstrap problem, and the bootstrap port might be the place to
search).
While we are there:
- removed a lot of debug which is now available using ktrace.
- reworked message handling to avoid mutliple copyin/copyout of the
same data. ktrace of Mach message now uses the in-kernel copy of the
message instead of copying it from userland.
- packed mach trap handlers arguments into a structure to avoid modifying
everything next time we have to add an argument.
