(PR#9908) Make AI understand channels

<URL: http://rt.freeciv.org/Ticket/Display.html?id=9908 >

> [per - Thu Sep 02 14:41:31 2004]:
> 
> On Sat, 21 Aug 2004, Gregory Berkolaiko wrote:
> > On Mon, 16 Aug 2004, Per Inge Mathisen wrote:
> > > I thought about adding ocean check to goto_is_sane(), but problem
is we
> > > might have a canal in a city. So I thought about making an aidata
matrix
> > > of canals that exist, but then I wondered if that was really worth the
> > > trouble...
> >
> > Yes, it is worth the trouble, I need it for ferry building, so
someone has
> > to do it.
> 
> Done. Patch attached.

It seems that the transitivity is not taken into account (i.e. A->B  and
 B->C  =>  A->C).

Also you can make it a single array by associating to each ocean the
smallest of the ocean numbers which are connected to it.  But I am not
sure if it's worth the trouble.

Gr