graph_sdl, physics_aux: handle USR1 signal, use in-place rotation

And remove incredibly annoying GCC warning spam. I damn near well known that the damn ABI has changed since 4.6. I know it by heart. Don't go reminding me damnit. It's damn annoying. But it's my damn fault - my processor has no damn fancy AVX extensions damnit. Damn. I better make myself a readline replacement. Or dunno.