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.
'generateBiomes()' constructs the biomemap as it generates biomes.
The biome calculated at first stone surface encountered is added to
the biomemap.
Previously, if no stone surface was encountered in a mapchunk column
the biomemap was left empty for that (x, z) position, causing biome
dust and water surface decoration placement to fail.
If at the base of a mapchunk column the biomemap is empty, add the
currently active biome to the biomemap, or if biome is NULL calculate
it for this position and add it to the biomemap.
In some configurations, such as when using the runit supervisor and its
tool chpst, the HOME variable might be unset. This resulted in an
unclear error message that was hard to pin down.
Fix 3 warnings reported by GCC 8.1 of the following type
```src/client/gameui.cpp:191:43: warning: « void* memset(void*, int, size_t) » effacement d'un objet du type non trivial « struct GameUI::Flags »; use assignment or value-initialization instead [-Wclass-memaccess]
memset(&m_flags, 0, sizeof(GameUI::Flags));
```
```
src/translation.cpp:43:16: warning: interception du type polymorphique « class std::out_of_range » par valeur [-Wcatch-value=]
} catch (std::out_of_range) {
```·
Because vein ore uses 3D noise (all the other ores use 2D noise) the
perlinmap Y size can be different in different mapchunks when close
to the ore Y limits.
Previously this caused bugs in the vein structure because changes in
perlinmap Y size did not recreate the noise objects.
Delete and recreate the noise objects with the new Y size if Y size
has changed.
Previously, the centering caused by the 'place center x/z' flags did
not take rotation into account. So schematics with unequal X and Z
dimensions were incorrectly placed. The bug was hidden for schematics
equal in X and Z dimensions.
Avoid crash in some situations when player is inside a node, causing
'above' to equal 'under'.
In this situation return 'under' which is the node position very close
to the face position that would normally be returned.
