This is an extension to the curses library.
It permits an application to determine if a string is currently bound
to any keycode.
RETURN VALUE
If the string is bound to a keycode, its value (greater than zero) is returned.
If no keycode is bound, zero is returned.
If the string conflicts with longer strings which are bound to keys, -1 is returned.
PORTABILITY
These routines are specific to ncurses. They were not supported on
Version 7, BSD or System V implementations. It is recommended that
any code depending on them be conditioned using NCURSES_VERSION.