IFp4 @1192291:

- Don't include sys/caprights.h, leverage the fact that cap_rights_t
  is also defined in sys/types.h.
- Include sys/types.h directly.
- For systems that do not have cap_rights_t, define it, so we can use
  it in au_to_rights() prototype.

Discussed with:	rwatson
Clean up shutdown_nice(). Just send the right signal to init(8).

Right now, init(8) cannot distinguish between an ACPI power button press
or a Ctrl+Alt+Del sequence on the keyboard. This is because
shutdown_nice() sends SIGINT to init(8) unconditionally, but later
modifies the arguments to reboot(2) to force a certain behaviour.

Instead of doing this, patch up the code to just forward the appropriate
signal to userspace. SIGUSR1 and SIGUSR2 can already be used to halt the
system.

While there, move waittime to the function where it's used; kern_reboot().
For GNU as, add two missing modes for each of the fcomip and fucomip
instructions.  Partially obtained from OpenBSD by Pedro Giffuni, while I
added the fcomip variants.

Apparently this should help with compiling certain variants of WebKit.

MFC after:	3 days
Need to test .MAKE.LEVEL everywhere before using it for bootstrapping
issues between fmake and bmake.
Thinko: don't forget to apply 'howto' in case init(8) isn't running.