Fix the hardware watchpoints on SMP amd64.  Load the updated %dr
registers also on other CPUs, besides the CPU which happens to execute
the ddb.  The debugging registers are stored in the pcpu area,
together with the command which is executed by the IPI stop handler
upon resume.

Reviewed by:	jhb
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Do not leak the NULLV_NOUNLOCK flag from the nullfs_unlink_lowervp(),
for the case when the nullfs vnode is not reclaimed.  Otherwise, later
reclamation would not unlock the lower vnode.

Reported by:	antoine
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Fix the wait6(2) on 32bit architectures and for the compat32, by using
the right type for the argument in syscalls.master.  Also fix the
posix_fallocate(2) and posix_fadvise(2) compat32 syscalls on the
architectures which require padding of the 64bit argument.

Noted and reviewed by:	jhb
Pointy hat to:	kib
MFC after:	1 week
Regenerate.