make Android double-click issue threshold smaller, close #2303
Merge branch 'stable' of https://github.com/Leaflet/Leaflet into stable

* 'stable' of https://github.com/Leaflet/Leaflet:
  Remove duplicate requestAnimFrame.
  Added test case for setView immediately after map is initialized
  Backported 9a2399ee500cfa24efd320e44c68ebf1c4109d78
  correctly remove event listener for layer control
backport #2503 fix false-positive drag on tap