Change the PF hash from Jenkins to Murmur3.  In forwarding tests
this showed a conservative 3% incrase in PPS.

Differential Revision:	https://reviews.freebsd.org/D461
Submitted by:	des
Reviewed by:	emaste
MFC after:	1 month
Make MAP_NOSYNC handling in the vm_fault() read-locked object path
compatible with write-locked path.  Test for MAP_ENTRY_NOSYNC and set
VPO_NOSYNC for pages with dirty mask zero (this does not exclude a
possibility that the page is dirty, e.g. due to read fault on
writeable mapping and consequent write; the same issue exists in the
slow path).

Use helper vm_fault_dirty() to unify fast and slow path handling of
VPO_NOSYNC and setting the dirty mask.

Reviewed by:	alc
Sponsored by:	The FreeBSD Foundation
Disable the invalid pointer test on FreeBSD

FreeBSD segfaults on invalid pointers passed to getcwd because it throbs the
address passed in in libc, whereas NetBSD just passes the information off to
the syscall, which allows the kernel to return EFAULT on bad pointers.

In collaboration with: pho
Sponsored by: EMC / Isilon Storage Division
Handle getting/setting niceness/priority correctly on FreeBSD vs NetBSD

This might be fallout from PR: 189821

Submitted by: pho
Sponsored by: EMC / Isilon Storage Division
SIGPWR does not exist on FreeBSD

Sponsored by: EMC / Isilon Storage Division
Make ctld start even if some LUNs are unable to open backing storage.

Such LUNs will be visible to initiators, but return "not ready" status
on media access commands.  If backing storage become available later,
`ctladm modify ...` or `service ctld reload` can trigger its reopen.