Fix 45deg rotation on some turrets

[FishyB]

Mortar and sniper. Something in 2.0 mesed up the diagonal because of railgun turrets.

Something about the cannon turrets seems unaffected so looky into it.

[FishyB]

Made a post to Factorio forums outlining this may be a bug.

Making the base not fixed means that it flips around if an enemy exits the viewing cone of a turret. Which is weird and unintended behaviour.