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.
Split some long lines.
Edit comments.
Remove unnecessary comments and unnecessary commented-out code.
Use std::fmax/fmin instead of MYMAX/MYMIN.
Remove scope-limiting braces.
Consistently define literals as floats, except in noise parameters.
Cleanup literals in noise parameters.
Remove unnecessary 'near_cavern' line.
Reduce max spawn y to be consistent with other mapgens.
Caverns first appeared in mgvalleys and were later added to other
mapgens as shared code. Now this shared code can replace mgvalley's
internal cavern code.
Also use shared tunnel code instead of internal code.
Changes to mapgen that will affect existing worlds (mgvalleys is not
stable):
Single lava and water sources not added in tunnels.
Previous caverns are unchanged but an equal number of new ones are
added at a distance from the previous.
From y = -256 to 192 nodes below, where the caverns taper at their
upper limit, they will have a slightly different shape as the taper
is now linear.
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.
* Fix many issues reported by clang-tidy
We have many issues in code related to some performance to float <-> double.
Clang-tidy reported it in performance-type-promotion-in-math-fn
I fixed many of them. It's not ready for a promote to blocking
Also fix some value which should be const-ref
