Don't include opt_vm86.h.

Remove vm86.

Pass 3.

Remove references to VM86 from the amd64 kernel configs.
VM86 mode isn't supported while in long mode.

PSL_AC is user-settable.

Remove PSL_MBO (the bits that Must Be One) from PSL_USER - which are the
bits that the 'user' can change.
Who knows what the effect of a user signal handler (which I think might have
access to the bi

Remove PSL_MBO (the bits that Must Be One) from PSL_USER - which are the
bits that the 'user' can change.
Who knows what the effect of a user signal handler (which I think might have
access to the bits) changing these bits might be!

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Define a PSL_CLEARSIG macro for the psl flags to be cleared on signal delivery
and use it everywhere.

Include PSL_D in the flags to be able to be set by the user. Since setmcontext
is used to restore context from a signal handler, this will allow restoring
PSL_D to what it was before the user code en

Include PSL_D in the flags to be able to be set by the user. Since setmcontext
is used to restore context from a signal handler, this will allow restoring
PSL_D to what it was before the user code entered the signal handler allowing
programs to work.

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Add PSL_T to PSL_USER; it's fine for a program to want to trap itself.

Move UCB-licensed code from 4-clause to 3-clause licence.

Patches provided by Joel Baker in PR 22364, verified by myself.

Move some files out of i386 into x86, so that they can be shared with
other ports.