returning just the first value of debug getlocal and getupvalue

the suggested access was to return nil always as the value, but these values aren't nil, and I felt it reasonable to return at least the variable name and not mislead that the value was nil

closes #1607

src/main/resources/assets/opencomputers/lua/machine.lua

@@ -938,7 +938,9 @@ sandbox = {
         }
       end
     end,
-    traceback = debug.traceback
+    traceback = debug.traceback,
+    getlocal = function(...) return (debug.getlocal(...)) end,
+    getupvalue = function(...) return (debug.getupvalue(...)) end,
   },
 
   -- Lua 5.3.