No longer use the unsuitable steel door/trapdoor sound.

Avoids player-placed leaves decaying when building while sneaking, which is common.

Register using the 'doors' mod API.

Increase noise resolution from 4 to 2 nodes for a higher quality
distribution.
Retune noise parameters to compensate for using eased noise.

Add an option, default disabled, to extend the collision boxes upwards.

broken by bb9279cc

default:river_water_source can also create sound if desired as
rivers are considered to be flowing water.
A simple mod for now, with the intention to later use new engine
environmental sound features if/when they appear.

rebased #2368 

Allows the initial hand registration to alter the 'wield_scale' without
needing to also alter it in creative mod.
Also make default mod a dependency again, as the initial hand
registration is required.

Previously, the value of 'mapgen_limit' was not used to limit the
spawn position.
If a friendly-biome spawn point is not found within a small world,
spawn point falls back to the engine spawn point, which has a larger
chance of success.

The output returned by `get_craft_result` has a replacements table that
contains any replacement items that could not be placed in the input
(due to the input stack having a count > 1). Put these replacements in
the dst list or drop them on the furnace.

This prevents a crash when a 'nil' digger is passed by the engine to
minetest.node_dig.

Engine change now makes this possible.