Add lavacooling sounds
Call on_rightclick from buckets
Add support for walkable plants
Mese and Diamond ore description consistancy.

Merely creates consistancy in the in-game naming of the ores.
Melting and freezing
Snow default level up
Update drowning

Needed if #851 gets merged
Fix typo in flower generation
Add mapgen_stair_cobble to minetest_game
Use 6d facedir to place upside down slabs and stairs
Longer range and insta-dig in creative
Remove mapgen_air alias
Merge remote-tracking branch 'upstream/master' into sponge
add spring