MFC r253603: zfs: move vnode creation from zfs_znode_cache_constructor
to zfs_znode_alloc
MFC r253606: zfs module: perform cleanup during shutdown in addition to
module unload
MFC r253772,253773,253989: dtrace disassembler: take the latest/last
CDDL code from OpenSolaris
MFC r253996,253997: opensolaris code: translate INVARIANTS to DEBUG and ZFS_DEBUG

Please note that support for compiling ZFS into a kernel is not in this
branch as of now.
MFC r253677,253679: make path matching in devfs rules consistent and
sane (and safer)