Make flag strings clear specified flag with 'no' prefix

Remove flagmask field from set_mapgen_params table
Add small bits of needed documentation
Tune block emerge and sending parameters to more aggressive values
Add capability to read table flag fields from Lua API
Define strlcpy on platforms that do not have it
ServerEnvironment: Remove direct dependency on EmergeManager
Fix possible missing unlock of env_lock
Add check to avoid usage of broken LuaJIT < 2.0.0beta8
Accept any error response code for missing index.mth
Add minetest.set_noiseparam_defaults() Lua API
Schematic: Add force_placement parameter to minetest.place_structure API
Fix broken cross-compiling
Fix g_settings not being included
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