Replace incomprehensive description of -m by much clearer text from OpenBSD, with the exception of one word.
Replace incomprehensive description of -m by much clearer text from OpenBSD,
with the exception of one word.

PR:		docs/112465
Submitted by:	naddy
Obtained from:	OpenBSD
MFC after:	1 week

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase