[#627] Fix some performance issues with me.pool

- Fixes the `arguments` deopt in V8
- Prevents the pool for `me.Color` from being emptied by application code (an optional argument for `getColor()` chooses to pull from the pool only for internal calls)
- Properly pushes the color back into the pool in `WebGLRenderer.clearSurface()`
Merge branch 'master' into ticket-591

Conflicts:
	src/video/webgl/webgl_renderer.js