MFC r306718:
Add history section for echo(1)
Sourced using the draft copy of the second edition manual
http://www.tuhs.org/Archive/PDP-11/Distributions/research/1972_stuff/unix_2nd_edition_manual.pdf

PR: 211785
Approved by: bcr (mentor)
Differential Revision: https://reviews.freebsd.org/D8104