Always escape user provided data in mainmenu fields
Fix lighting artifacts (Issue #1887).
Fix struct vs. class in forward declarations
Optimize noise implementations
Fix compiler warning (signed vs. unsigned)
Biomes: Make biome heat and humidity noise parameters user-configurable
Noise: Update Noise::resizeNoiseBuf to account for lacunarity not equal to 2
Fix builds failing on BSD-like (such as OSX) due to an irrlicht bug (temporary fix)

Details:
- https://sourceforge.net/p/irrlicht/bugs/433/
- https://github.com/minetest/minetest/issues/1687#issuecomment-61368769
- https://forum.minetest.net/viewtopic.php?f=42&t=9190&start=125#p159364

In case when "settings.h" is included from "emerge.cpp" or
"environment.cpp", u64 type has "unsigned long" length because
previously <stdint> was included. When "settings.h" is included from
"settings.cpp", u64 has "unsigned long long" length because no <stdint>
was included previously. This leads to different signatures of "setU64" method
and linker cannot find appropriate symbol.

The best fix of this bug should be done in the Irrlicht, but as hotfix I
think this is OK and better than types changing.

Previously this bug didn't appear because there was no "settings.cpp" file and
implementation of all methods was done in the header file.
Increase performance of getLight() by at least 2x

Leads to the following increases:
getSmoothLight() approx.     40% increase
getTileInfo() approx.        25% increase
MapBlockMesh::MapBlockMesh() 25-30%
Ignore .name directories and files

Signed-off-by: Craig Robbins <kde.psych@gmail.com>
Rewrite fs:GetDirListing(file) by kahrl
Settings: Make setting entry group and values mutually exclusive

This greatly reduces the complexity of Settings code.
Additionally, several memory leaks were fixed.