try to fix occasional flickering. only seen on nexus with PowerVR
-> clear stencil region by drawing a quad instead of using glClear(stencil) for each tile
docs
return if shader program has changed
- handle limiting of unused loaded tiles in limitCache
- remove unused tiles based on distance to map center
Merge branch 'master' of git@github.com:hjanetzek/VectorTileMap.git