Readline -- cannot bind to both Ctrl-tab and tab at the same time?

[random832 at fastmail.us]

On Sun, Jun 28, 2015, at 14:55, Steven D'Aprano wrote:
> I'm trying to use a readline binding for both TAB and Ctrl-TAB, but it's
> not
> working for me. Whichever I install second seems to over-ride the first.

Can you bind it directly to whatever escape sequence ctrl-tab produces?
Some terminals may not be able to generate an escape sequence for
ctrl-tab, or may require a special option to be enabled (e.g.
modifyOtherKeys for xterm).