Avoid missed narrowing warnings.
Fix mismatched function signatures.
Merge branch 'compilation' into develop
Use new-style full screen.

Create a borderless window covering the whole screen. Don't change the
actual screen resolution. Change the resolution of the OpenGL view's
backing store.
Real HiDPI support.

Create high-resolution OpenGL backing stores (windowed mode only, for
now).  Ships should display at twice the resolution as before on HiDPI
screens, when the sprites support it.
Merge branch 'hidpi' into develop