Bump libzfs.so and libzpool.so versions

Bump the library versions as advised by the libtool guidelines.

https://www.gnu.org/software/libtool/manual/html_node/Updating-version-info.html

Two new functions were added but no existing functions were changed,
so we increase the version and the age (version:revision:age).

Added functions (2):
- boolean_t zpool_is_draid_spare(const char *);
- zpool_compat_status_t zpool_load_compat(const char *,
      boolean_t *, char *, char *);

Additionally bump the libzpool.so version information.  This library
is for internal use but we still want to update the version to track
major changes to the interfaces.

The libzfsbootenv, libuutil, libnvpair and libzfs_core libraries
have not been updated.

Reviewed-by: Richard Laager <rlaager@wiktel.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #11817

lib/libzfs/Makefile.am

@@ -87,7 +87,7 @@ if BUILD_FREEBSD
 libzfs_la_LIBADD += -lutil -lgeom
 endif
 
-libzfs_la_LDFLAGS += -version-info 4:0:0
+libzfs_la_LDFLAGS += -version-info 5:0:1
 
 include $(top_srcdir)/config/CppCheck.am