Improve support for XSAVE with debuggers.
- Dump an NT_X86_XSTATE note if XSAVE is in use. This note is designed
  to match what Linux does in that 1) it dumps the entire XSAVE area
  including the fxsave state, and 2) it stashes a copy of the current
  xsave mask in the unused padding between the fxsave state and the
  xstate header at the same location used by Linux.
- Teach readelf() to recognize NT_X86_XSTATE notes.
- Change PT_GET/SETXSTATE to take the entire XSAVE state instead of
  only the extra portion. This avoids having to always make two
  ptrace() calls to get or set the full XSAVE state.
- Add a PT_GET_XSTATE_INFO which returns the length of the current
  XSTATE save area (so the size of the buffer needed for PT_GETXSTATE)
  and the current XSAVE mask (%xcr0).

Differential Revision:	https://reviews.freebsd.org/D1193
Reviewed by:	kib
MFC after:	2 weeks
Merge from CheriBSD (3422ebe71b6c06fe78b1be73623b240c219e08e3):

Rename beripic to beripic0.

MFC after:	1 week
Sponsored by:	DARPA, AFRL
Prevent overflow issues in timeout processing

Previously, any timeout value for which (timeout * hz) will overflow the
signed integer, will give weird results, since callout(9) routines will
convert negative values of ticks to '1'. For unsigned integer overflow we
will get sufficiently smaller timeout values than expected.

Switch from callout_reset, which requires conversion to int based ticks
to callout_reset_sbt to avoid this.

Also correct isci to correctly resolve ccb timeout.

This was based on the original work done by Eygene Ryabinkin
<rea@freebsd.org> back in 5 Aug 2011 which used a macro to help avoid
the overlow.

Differential Revision:	https://reviews.freebsd.org/D1157
Reviewed by:	mav, davide
MFC after:	1 month
Sponsored by:	Multiplay