Fix compatibility with Cleanroom Loader 0.2.3
Update Mixin to 0.8.7
Update MixinExtras to 0.4.1
Note: Currently Non-Cleanroom MixinBooter loads MixinExtras 0.3.6 first, so newer 0.3.6+ features should not be depended on until MixinBooter updates if full compatibility with all mods is desired