GDB fails to build with Python 3.7

[Paul.Koning@dell.com]

> On May 30, 2018, at 6:26 PM, Joel Brobecker <brobecker@adacore.com> wrote:
> 
> From what I can tell, this was was introduced when you added
> Python 3.x support, back in 2012:
> 
>    commit 9a27f2c60d760a95a27e336750f26f69f91dd156
>    Date:   Wed Dec 12 16:47:30 2012 +0000
>    Subject: Add support for Python 3
> 
> Do you remember why you added that _PyImport_FixupBuiltin call?

I just submitted a proposed patch for this.  It's pretty easy, I'm not
sure how I missed it originally.  Possible the documentation has
improved in the meantime.

	paul