Currently, when bsd.port.mk outputs a message addressed to a user, it would
typically pipe it through ${FMT} 75 79 command to ensure that if it gets
overly long, it would be wrapped nicely. Do the same when outputting IGNORE
message which often gets very long. While here, add missing section number
in sed(1) references in comments.

Differential Revision: D4116
Approved by: portmgr (bapt)