Ada and x86_64

[Robert Dewar]

We have not ported GNAT to 64bit Alpha Linux, though I believe someone else
has done this port.

Honza said:

> Is that dificult even in the case that Linux port exists?  I would expect there
> to already be working 64bit Alpha Linux vesion (or not?) so the stuff can just
> be merged together, I hope.

That would certainly be a reasonable first step, and the machines are both
little endian, which helps.