8067 zdb should be able to dump literal embedded block pointer

illumos/illumos-gate@4923c69fddc0887da5604a262585af3efd82ee20
https://github.com/illumos/illumos-gate/commit/4923c69fddc0887da5604a262585af3efd82ee20

https://www.illumos.org/issues/8067

Add an option to zdb to print a literal embedded block pointer supplied on the
command line:
zdb -E [-A] word0:word1:...:word15

Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Alex Reece <alex@delphix.com>
Reviewed by: Yuri Pankov <yuri.pankov@gmail.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: Matthew Ahrens <mahrens@delphix.com>