Weather support

builtin/falling.lua

doc/lua_api.txt

minetest.conf.example

src/content_abm.cpp

src/defaultsettings.cpp

src/emerge.cpp

src/environment.h

src/game.cpp

src/map.cpp

src/map.h

src/mapblock.cpp

src/mapblock.h

src/mapnode.cpp

src/mapnode.h

src/nodedef.cpp

src/nodedef.h

src/script/common/c_content.cpp

src/script/cpp_api/s_node.cpp

src/script/cpp_api/s_node.h

src/script/lua_api/l_env.cpp