/PERMIT_INPUT="hot-key-defintion"

   Hot-key used to permit a watcher (who is not normally able to have
   keyboard control) to acquire temporary keyboard control through
   use of his REQUEST_INPUT hot-key.

   PERMIT_INPUT can be issued by the user being watched, or by a primary
   watcher who currently has keyboard control.

   To successfully grant PERMIT_INPUT, the user granting it must
   currently have keyboard control (via either SIMULTANEOUS_INPUT
   or TOGGLE_INPUT).

   If a PERMIT_INPUT request is rejected (due to not currently having
   control of the keyboard) then the terminal bell will beep.

   Once PERMIT_INPUT has been enabled and a watcher then accepts it (by
   using his REQUEST_INPUT hot-key), the watcher and the user who
   permitted him may either toggle input between themselves using their
   TOGGLE_INPUT hot-keys, or may both type simultanously if the PSIMUL
   qualifier (or default) is in effect for the permitted watcher. (See
   also PNOBEEP.)

   Once granted, PERMIT_INPUT can be revoked again at any time by
   issuing another PERMIT_INPUT. (The PERMIT_INPUT key toggles
   PERMIT_INPUT on and back off.)

   A PERMIT_INPUT granted by the user being watched is also revoked
   whenever the primary watcher (if any) toggles input.

   Likewise, a PERMIT_INPUT granted by a primary watcher is revoked
   whenever the user being watched toggles input.

   Thus input-ability gained through PERMIT_INPUT/REQUEST_INPUT is very
   temporary.

   The logical WATCHER$PERMIT_INPUT specifies the default hot-key value
   for a primary watcher, and the logical USER$PERMIT_INPUT specifies
   the default hot-key value for use when being watched.

   Note that PERMIT_INPUT and REQUEST_INPUT may be used to temporarily
   grant input-ability to a watcher who otherwise would not be able to
   gain keyboard control due to keyboard-control licensing-option
   or ALLOW-command restrictions.