mcopt 0.2.0-alpha.2

Second alpha of mcopt.

• Distant Horizons no longer crashes. mcopt detects it and stays on OpenGL, so it runs without the Metal renderer's speedup; mcopt's other optimizations stay on.
• Lighting and texture handling allocate less, so there's less garbage-collection work.
• Far terrain (experimental): less flicker where far terrain hands off to real chunks.
• Launching with -Dmcopt.profile=none no longer writes profile=alpha into config/mcopt.properties.

Still alpha: expect bugs, and back up your worlds.