Enabled TUI mode on MSYS2

[Eli Zaretskii]

> Cc: GDB Patches <gdb-patches@sourceware.org>
> From: Pedro Alves <palves@redhat.com>
> Date: Wed, 14 Sep 2016 19:36:23 +0100
> 
> On 09/14/2016 07:32 PM, Giah de Barag wrote:
> 
> > Pedro: Seeing that Eli is able to build and run GDB with the new
> > readline, we should be able to move forward. I am willing to help.
> > What do you need from us to move this forward?
> 
> See the url I pointed at and the discussion surrounding it.
> Someone needs to investigate the issues Patrick originally
> stumbled on, and come up with some way to fix them.

Yes.  But if importing a newer Readline is not going to happen soon, I
think we should apply my patches to our copy of Readline, to avoid
these issues.