Item entities only have their gravity ticked every 4 ticks when on ground.
Fix that and also remove Spigot's arbitrary tick skipping. It's a terribly
cheap way of getting extra performance that doesn't really work at all.
Make sure the hash code does not change and also remove outdated
equals logic from CraftPlayer. Long-term, the override there should
be entirely removed, but this is good enough for now.
Replacing some getHandle method calls with direct field access will
also reduce overhead from casts that the overridden methods come with,
at least until those are changed later on as well.
Nassim Jahnke