Fix build
Note: this does not fix the warnings generated by clang
Fix node 0,0,0 being highlighted when enable_node_highlighting == false

Without this patch node 0,0,0 is highlighted when enable_node_highligting is false
There is a minor lighting issue remaining, however it seems to be related to a different bug (https://github.com/minetest/minetest/issues/1887)
Fix settings callback "call" lost on rebase
Add fontengine.cpp to Android.mk
Fix style of comment in minetest.conf.example
Use setting groups for NoiseParams

Add format example to minetest.conf.example
Add Settings::setU16()
Throw exception on attempted access of NULL settings groups
Settings: Fix getNoiseParamsFromValue()
Add definable node_stone to biome API, mgv5, mgv7. Reduce and correct depth of mgv7 biomes. l_mapgen.cpp: add '#include mapgen_v5.h' because '#include mapgen_v7' is there. Improve underwater grass hack
Settings: Various setting group fixes and enhancements

 - Remove blank setting values when setting has a group
 - Pair setting values with groups in file when possible
 - Preserve user-set whitespace in setting objects
 - Delete setting value when setting NoiseParams group
 - Delete overwritten groups outside of lock