Function: enable-flow-control-on

Enable flow control if using one of a specified set of terminal types.
Use `(enable-flow-control-on "vt100" "h19")' to enable flow control
on VT-100 and H19 terminals. When flow control is enabled,
you must type C-\ to get the effect of a C-s, and type C-^
to get the effect of a C-q.