Fix undeclared global variable
minetest.env:* --> minetest.*
(only in minetest_game base mods, others to follow separately)
update display_blocks
update currency
update future_ban
remove hovercraft mod
update item_tweaks
update jumping
update locks
update markers
update memorandum
update pipeworks
update prefab
update replacer
updated steel
update technic
update titanium
update tpr
update travelnet
update ufos