[r7312] SDL2 Crash on quick window resize

[firefrorefiddle]

I compiled simutrans from trunk. When I choose SDL2 as a backend, I experience crashes if the window is resized quickly.

This is easily reproduced by either:
a) starting simutrans and clicking the "full screen" icon in the title bar.
b) grabbing the window border and dragging it quickly.

This may be related to a certain window size. My screen is 2550x1440 pixels, and I can only get it to crash when I resize the window to something approximately wider than half of either my total screen width or height. However, if I resize slowly then I can fill the entire screen and there doesn't seem to be any instability.

Terminal output on crash is "Segmentation fault".

Problem goes away if I switch to SDL as a backend. This is on Linux 3.13, using a Mobility Radeon HD 5800 Series graphics card and Catalyst 13.35.5 drivers.