blocked in the kernel. The task that catched the exception may unblock
it by sending a reply to the exception message (Of course it will have
to change something so that the exception is not immediatly raised again).
Handling of this reply is a bit complicated, as the kernel acts as the
client instead of the server. In this situation, we receive a message
but we will not send any reply (the message we receive is already a reply).
I have not found anything better than a special case in
mach_msg_overwrite_trap() to handle this.
A surprise: exceptions ports are preserved accross forks.
While we are there, use appropriate 64 bit types for make_memory_entry_64.
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