[Freeciv-Dev] (PR#2396) isotrident hills/forests/mountains are broken

["Jason Short via RT" <rt@xxxxxxxxxxxxxx>]

In isotrident, the hills, forests, and mountains extend below the tile. 
  Occasionally this works - for instance the mountains (and probably 
forests) are usually covered up by the terrain in front.  But it 
certainly doesn't always work.  Look at

http://rt.freeciv.org/Ticket/Attachment/16872/10054/mountainous.png

The mountains in the middle have the bottom part of the sprite cut off - 
overwritten by the hills there (this is under the mountainous patch, 
PR#2378).  And you can see the hills in the very top draw all over each 
other.

This is a critical issue, since it means changes to the drawing code 
will make break things badly.

jason