man: document ShowStatus and SetShowStatus()

man: document ShowStatus and SetShowStatus()

SetShowStatus() was added in order to fix #11447. Recently, I ran into
the exact same problem that OP was experiencing in #11447. I wasn’t able
to figure out how to deal with the problem until I found #11447, and it
took me a while to find #11447.

This commit takes what I learned from reading #11447 and adds it to the
documentation. Hopefully, this will make it easier for other people who
run into the same problem in the future.