Fix markup.

MFC after:	1 month
Sponsored by:	The FreeBSD Foundation
Update llvm patches for r274286 and r275633 so all the tests will pass.
MFV r247174:

Expose arc_meta_limit, et al via kstats.

Note that as a result, vfs.zfs.arc_meta_used is removed.
The existing vfs.zfs.arc_meta_limit sysctl/tunable is retained
with a SYSCTL_PROC wrapper.

Illumos ZFS issues:
    3561 arc_meta_limit should be exposed via kstats

Relnotes:	yes
MFC after:	2 weeks
Add _NEW flag to mtx(9), sx(9), rmlock(9) and rwlock(9).
A _NEW flag passed to _init_flags() to avoid check for double-init.

Differential Revision:	https://reviews.freebsd.org/D1208
Reviewed by:	jhb, wblock
MFC after:	1 Month
Fix quick_exit(3) manual page to match reality - the status was missing.

MFC after:	1 month
Sponsored by:	The FreeBSD Foundation