Sync with upstream r315983.

Move files originating from upstream below "dist/":

  OPENSOLARIS.LICENSE -> dist/OPENSOLARIS.LICENSE
  usr.sbin/zdb/zdb.8 -> dist/cmd/zdb/zdb.8
  sbin/zfs/zfs.8 -> dist/cmd/zfs/zfs.8
  sbin/zpool/zpool-features.7 -> dist/cmd/zpool/zpool-features.7
  sbin/zpool/zpool.8 -> dist/cmd/zpool/zpool.8
  include/libintl.h -> dist/head/libintl.h
  include/stdio_ext.h -> dist/head/stdio_ext.h
  include/thread.h -> dist/head/thread.h
  sys/kern/callb.c -> dist/uts/common/os/callb.c
  sys/kern/fm.c -> dist/uts/common/os/fm.c
  sys/sys/extdirent.h -> dist/uts/common/sys/extdirent.h
  sys/sys/isa_defs.h -> dist/uts/common/sys/isa_defs.h
  sys/sys/procset.h -> dist/uts/common/sys/procset.h
  sys/sys/sysmacros.h -> dist/uts/common/sys/sysmacros.h

Adapt "usr.sbin/fstyp/Makefile".

external/cddl/osnet/dist/uts/common/sys/extdirent.h

@@ -1,4 +1,4 @@
-/*	$NetBSD: extdirent.h,v 1.1 2009/08/07 20:57:57 haad Exp $	*/
+/*	$NetBSD: extdirent.h,v 1.1 2019/06/24 08:27:20 hannken Exp $	*/
 
 /*
  * CDDL HEADER START

usr.sbin/fstyp/Makefile

@@ -1,4 +1,4 @@
-#	$NetBSD: Makefile,v 1.4 2019/06/22 09:48:39 hannken Exp $
+#	$NetBSD: Makefile,v 1.5 2019/06/24 08:27:21 hannken Exp $
 
 .include <bsd.own.mk>
 
@@ -21,6 +21,7 @@ COPTS.zfs.c+=	-Wno-strict-prototypes
 COPTS.zfs.c+=	-I${NETBSDSRCDIR}/external
 COPTS.zfs.c+=	-I${NETBSDSRCDIR}/external/cddl/osnet/include
 COPTS.zfs.c+=	-I${NETBSDSRCDIR}/external/cddl/osnet/sys
+COPTS.zfs.c+=	-I${NETBSDSRCDIR}/external/cddl/osnet/dist/head
 COPTS.zfs.c+=	-I${NETBSDSRCDIR}/external/cddl/osnet/dist/lib/libzpool/common
 COPTS.zfs.c+=	-I${NETBSDSRCDIR}/external/cddl/osnet/dist/uts/common
 COPTS.zfs.c+=	-I${NETBSDSRCDIR}/external/cddl/osnet/dist/uts/common/fs/zfs