Explosions near the wrap-around border only destroy one side of the landscape

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What steps will reproduce the problem?
1. Create any map where you have a lot of land near the right and left border, 
ideally they have nearly or exactly the same height (it should be easy to walk 
or jump over)
2. Start a game with wrap-around turned on, a lot of heavy weapons for testing 
and optionally infinite attacks (for convenience)
3. Get a hedgehog near the border of the map
4. Place a dynamite or a similar explosive near the border

What is the expected output? What do you see instead?
I expect the explosion would destroy land on both sides from the border. But 
actually, the explosion will always only destroy land of one side of the 
border: The side where you placed the dynamite. This leads to odd half-circle 
shapes. It is also quite odd that you can place a dynamite very close to the 
border, just walk a few steps to pass the border and the dynamite explodes near 
the hog completely harmlessly.

What version of the product are you using? On what operating system?
I use GNU/Linux and can reproduce this in Git f488421…

Please provide any additional information below.
This is part of a series of weird things which happen near the border in 
wrap-around worlds.

Original issue reported on code.google.com by almikes@aol.com on 10 Dec 2014 at 6:25

[GoogleCodeExporter]

Hrm. So, most of these wrap things are 'cause coords aren't actually wrapped.  
But... This one I kinda like strategically, since you can jump through the 
border to attack, then jump back.  Makes the border something a bit more than 
just a seamless transition of the world.

But yeah, most odd border behaviour is 'cause it works more like portal.

Original comment by kyberneticist@gmail.com on 10 Dec 2014 at 4:45