Use MO's name consistently (Mel L. O'Cat), fixes #1146
Use MO's name consistently (Mel L. O'Cat), fixes #1146

Use MO's name consistently everywhere, per suggestion
from @benjub.

Signed-off-by: David A. Wheeler <9ae72d22d8b894b865a7a496af4fab6320e6abb2@dwheeler.com>

metamath/set.mm,metamath/set.mm,metamath/set.mm