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.
It turns out there is no need to return the new value and
preserve the old one in random_turn, the procedure can be
made to modify the value in-place. This saves quite a bunch
of parameter and return value copying.
Previously only 'mapgen water source' and 'mapgen river water source'
were checked for. Games can use multiple liquid nodes defined for biomes,
many of which will not be aliased to those 2 mapgen aliases, causing
floating dungeons to generate in some liquids.
Now we check for liquid drawtype instead, so can remove liquid nodes
from dungeonparams.
Also check for 'airlike' drawtype instead of 'CONTENT_AIR' to avoid
generation in 'airlike' nodes in some rare situations. This will also be
needed for when we add definable biome air nodes.
* Rename IWritableNodeDefManager to NodeDefManager
* Make INodeDefManager functions const
* Use "const *NodeDefManager" instead of "*INodeDefManager"
* Remove unused INodeDefManager class
* Merge NodeDefManager and CNodeDefManager
* Document NodeDefManager
