Luis Javier Merino authored Jul 18, 2022 and Kurt Hindenburg committed Jul 19, 2022

For clarity, the VT state machine has some comments where it differs
from the diagram from vt100.net. Add comments for some transitions on
String Terminator (ST / 0x9C) which appear on the diagram, but which
were already handled in the "anywhere" state.

(cherry picked from commit 05a4d489)