Add comments in db about SQL injection needing to be fixed

mods/db/init.lua

@@ -68,6 +68,7 @@ assert(itb_db:exec[[
 db = {}
 
 function db.player_get_meta(name)
+  -- FIXME use http://luasqlite.luaforge.net/lsqlite3.html#db:prepare to prevent SQL injection
 	for row in itb_db:nrows("SELECT meta FROM player WHERE name = '" .. name .. "';") do
 		return minetest.parse_json(row.meta)
 	end
@@ -77,6 +78,7 @@ function db.player_get_meta(name)
 end
 
 function db.player_put_meta(name, meta)
+  -- FIXME use http://luasqlite.luaforge.net/lsqlite3.html#db:prepare to prevent SQL injection
 	local r = itb_db:exec("REPLACE INTO player_meta (name, meta) VALUES ('" .. name .. "', '" ..
 		minetest.write_json(meta) .. "');")
 	if not r then