vtysh: fix build against readline 6.3

readline 6.3 removes some old deprecated funnily-named types.  This
updates vtysh to use the new types so it builds again.

Reported-by: Joel Teichroeb <klusark@archlinux.invalid>
References: https://bugs.archlinux.org/task/39495
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
1 file changed