v6 always last to discourage selection.
Special mapgens flat, fractal, singlenode, next to last. Of these, singlenode
last to discourage selection.
Of the remaining, v5 last due to age, v7 first due to being the default.
Biome-defined dungeon nodes was added as a feature to MT 5.0.0.
So now remove most of the hardcoded dungeon node code that assumes a
game has stone, sandstone, desert stone, and no other stone types.
If biome-defined dungeon nodes are not found, dungeon nodes fall back
to the 'cobble' mapgen alias if present, if not present they fall back
to biome-defined 'stone'.
Remove now-unnecessary mapgen aliases from MapgenBasic. Non-mgv6 games
now only need to define 3 to 5 mapgen aliases.
Document dungeon parameters.
Make c_lava_source fallback to c_water_source as both are used as cave
liquids.
Add user-settable noise parameters for dungeon density to each mapgen,
except V6 which hardcodes this noise parameter.
Move the calculation of number of dungeons generated in a mapchunk out
of dungeongen.cpp and into mapgen code, to allow mapgens to generate
any desired number of dungeons in a mapchunk, instead of being forced
to have number of dungeons determined by a density noise.
This is more flexible and allows mapgens to use dungeon generation to
create custom structures, such as occasional mega-dungeons.
Previously the only way to disable biomes was to 'clear' the registered
biomes in a mod, but this method causes large amounts of unnecessary
processing:
1. Calculation of 4 2D noises.
2. Looping through all nodes of a mapchunk replacing nodes with identical
nodes.
The new flag disables those operations.
Previously, caverns confused tunnel generation causing biome top and filler
nodes to appear in caverns.
Split 'generateCaves()' into 2 functions to separate tunnel and large
randomwalk cave generation.
In each mapgen re-order cave generation to generate tunnels before caverns.
Add new biome fields 'node_dungeon', 'node_dungeon_alt', 'node_dungeon_stair'.
If 'node_dungeon' is not defined dungeons fall back to classic behaviour.
Remove messy and imprecise dungeon material code from 'generateBiomes()'.
Code deciding dungeon materials is now in 'generateDungeons()' and uses the
biome at mapchunk centre for more precision.
Remove hardcoded 'MG_STONE' types as long intended.
* Rename IWritableNodeDefManager to NodeDefManager
* Make INodeDefManager functions const
* Use "const *NodeDefManager" instead of "*INodeDefManager"
* Remove unused INodeDefManager class
* Merge NodeDefManager and CNodeDefManager
* Document NodeDefManager
