Illumos #1888: zfs(8) should mention zfs recv -e

Reviewed by: Garrett D'Amore <garrett@damore.org>
Reviewed by: Eric Schrock <eric.schrock@delphix.com>
Reviewed by: Gordon Ross <gordon.w.ross@gmail.com>
Approved by: Richard Lowe <richlowe@richlowe.net>

References:

https://www.illumos.org/issues/1888

Ported by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #683