document stty -g code positions

[jidanni]

In (info "(coreutils)stty invocation"), please mention what all the
secret codes in stty -g (--save) are.

One could see e.g., right away that position 15 is different on my
mom's terminal, but what stty setting is position 15, one asks?

Otherwise one has to do e.g.,
COLUMNS=1 stty -a > /tmp/ww
COLUMNS=1 stty -a -F /dev/tty1|diff - /tmp/ww
to see what the differences are for two terminals.

You can mention that the positions are version dependent, and not to
be sent to one's friends expecting them to work.