add packages for libufs, libzfs

currently FreeBSD-utilities depends on both FreeBSD-ufs and FreeBSD-zfs.
this is not desirable, because those are both relatively large packages
and the user may want to remove one or the other – or perhaps both, e.g.
in a jail or embedded system.

the reason for this dependency is that fstyp(8), which is in
FreeBSD-utilities, links both libufs and libzfs.  FreeBSD-utilities is
the correct place for fstyp, so we don't want to move that.

instead, add two new packages: libufs contains libufs, and libzfs
contains libzfs plus the ZFS libraries it depends on: libavl, libnvpair,
libspl, libtpool, libumem, libuutil, libzfs_core and libzutil.

with this change, it is possible to remove FreeBSD-ufs and/or
FreeBSD-zfs while leaving FreeBSD-libufs, FreeBSD-libzfs and
FreeBSD-utilities installed.

Reviewed by:	manu, des
Approved by:	des (mentor)
Differential Revision:	https://reviews.freebsd.org/D50148

cddl/lib/libavl/Makefile

@@ -1,6 +1,6 @@
 .PATH: ${SRCTOP}/sys/contrib/openzfs/module/avl
 
-PACKAGE=	zfs
+PACKAGE=	libzfs
 LIB=	avl
 LIBADD=	spl
 SRCS=	avl.c

cddl/lib/libnvpair/Makefile

@@ -5,7 +5,7 @@
 LIB=	nvpair
 LIBADD=	spl
 
-PACKAGE=	zfs
+PACKAGE=	libzfs
 # user
 INCS=	libnvpair.h
 SRCS=	libnvpair.c \

cddl/lib/libspl/Makefile

@@ -6,7 +6,7 @@
 
 LIB=	spl
 LIBADD=
-PACKAGE=	zfs
+PACKAGE=	libzfs
 
 SRCS = \
         assert.c \

cddl/lib/libtpool/Makefile

@@ -4,7 +4,7 @@
 
 LIB=	tpool
 LIBADD=	spl
-PACKAGE=	zfs
+PACKAGE=	libzfs
 
 INCS=	thread_pool_impl.h
 SRCS=	thread_pool.c

cddl/lib/libumem/Makefile

@@ -1,6 +1,6 @@
 .PATH: ${SRCTOP}/cddl/compat/opensolaris/lib/libumem
 
-PACKAGE=	zfs
+PACKAGE=	libzfs
 LIB=	umem
 SRCS=	umem.c
 WARNS?=	3

cddl/lib/libuutil/Makefile

@@ -1,6 +1,6 @@
 .PATH: ${SRCTOP}/sys/contrib/openzfs/lib/libuutil
 
-PACKAGE=	zfs
+PACKAGE=	libzfs
 LIB=	uutil
 SRCS=\
 	uu_alloc.c \

cddl/lib/libzfs/Makefile

@@ -7,7 +7,7 @@
 .PATH: ${SRCTOP}/sys/contrib/openzfs/module/zstd
 .PATH: ${SRCTOP}/sys/contrib/openzfs/module/zstd/lib
 
-PACKAGE=	zfs
+PACKAGE=	libzfs
 LIB=	zfs
 LIBADD= \
 	avl \

cddl/lib/libzfs_core/Makefile

@@ -6,7 +6,7 @@
 
 LIB=	zfs_core
 LIBADD=	nvpair spl zutil
-PACKAGE=	zfs
+PACKAGE=	libzfs
 
 INCS=	libzfs_core.h
 SRCS=	libzfs_core.c \

cddl/lib/libzutil/Makefile

@@ -4,7 +4,7 @@
 
 LIB=	zutil
 LIBADD=	avl geom m tpool
-PACKAGE=	zfs
+PACKAGE=	libzfs
 
 INCS = zutil_import.h
 

lib/libufs/Makefile

@@ -1,4 +1,4 @@
-PACKAGE=	ufs
+PACKAGE=	libufs
 LIB=	ufs
 SHLIBDIR?= /lib
 SHLIB_MAJOR=	8