[Freeciv-Dev] (PR#6356) move the origin tile of the mapview

["Jason Short" <jdorje@xxxxxxxxxxxxxxxxxxxxx>]

Currently the origin tile (mapview_canvas.map_[xy]0) has its top corner 
(of the diamond-shaped tile) at (0,0).  This means the left half of the 
tile is not shown at all.  See old.png (sent to RT separately).

The core problem is that this is assymetric and inelegant.  I don't like it.

A more concrete problem is what happens when you have non-standard 
topologies.  For instance with a map that doesn't wrap in the X 
directionthe top-left corner of the mapview cannot be aligned with the 
map.  This is a symptom of the assymetry.

The form that makes topology compatability easiest has the top-left 
corner of the bounding box of the x0,y0 tile at (0,0).  Now we can align 
both left and top sides of the mapview with a non-wrapping iso-map.  See 
new.png (sent to RT separately).

jason