[Freeciv-Dev] (PR#16592) zooming using cairo

["Jason Short" <jdorje@xxxxxxxxxxxxxxxxxxxxx>]

<URL: http://bugs.freeciv.org/Ticket/Display.html?id=16592 >

This is a quick hack to implement very rough zooming using cairo.
Naturally it requires the cairo patch.  Then you can zoom in or out
using the view menu.  Several things don't work at all (things get drawn
in the wrong place and/or without zoom); this is because of the way the
core drawing code works and will not be easy to fix (this is why I want
the core drawing code to use cairo).  Your best results will be from
testing it on an empty map.

It is surprisingly fast on my machine.  However in addition to the
aforementioned problems there are also anti-alias artifacts at the tile
borders.  Not sure what's up with these.

-jason