[mcl_tbs] - stronghold and nether-fortress generators, depends on mineclonia/voxelibre, tbs

uses the async environment, structure is deterministic between threads, but there is a chance of tiles getting cut near mapchunk border when emerge_threads > 1
WIP: see --FIXME and --TODO inside the code
please check the debug variables at the top of each file
unzip and put both mods side by side in the mods directory