Log warning of unused mods when dependencies are missing

hazmat_suit/depends.txt

@@ -1,2 +1,2 @@
 3d_armor
-technic
+technic?

hazmat_suit/init.lua

@@ -1,3 +1,8 @@
+if not minetest.get_modpath("technic") then
+	minetest.log("warning", "hazmat_suit: Mod loaded but unused.")
+	return
+end
+
 local part_count = 4
 
 local level = 35