Pause when pal() called for first time

[jtothebell]

The first time the palette is shifted, there is a pause because the sprite sheet has to be re-rendered and it is not fast enough. It may be possible to optimize it further, or find a different way to shift the palette. PicoLove uses shaders, but shaders are not yet supported by lovepotion, and as of now there is no plans to add support.