fix iOS device rotation

[incanus]

Rotating device changes aspect ratio on the fly and GL context needs to compensate. Disabling in app for now.

[kkaefer]

• We should update the dimensions mid-rotation, not at the beginning, to decrease the initial distortion
• There is a black flicker when rotation begins

[kkaefer]

This used to be fixed by moving to GLKViewController. However, I reverted this change and when you now turn the device, the screen turns black until you touch it.

I suspect that iOS allocates/changes to a new framebuffer once you turn the device and displays it. We somehow need to intercept that and force an immediate render before the new buffer is displayed to avoid a black flicker.

[incanus]

This no longer happens. Related: cutting-room-floor/mapbox-gl-cocoa#20