Leaflet leaks memory on iOS 7

iOS7 Safari crashes too fast on Leaflet 0.6 (e.g. clustering 3000 markers), while it's not on 0.5.1 (even with 10000).

Original issue: https://github.com/Leaflet/Leaflet.markercluster/issues/254
Commit that introduces the leak: https://github.com/Leaflet/Leaflet/commit/8e65fe7a89f69c48fbe4f06111102f54508e5401
Related pull request: https://github.com/Leaflet/Leaflet/pull/1514
