translator: changed done stack to standard stack

push calls replaced with emplace calls, which required the done item
class to have constructors, one for each possible present arguments of
just rpn item, rpn item and last token, and rpn item with both first and
last tokens (the old done stack class was replaced with a using alias);
pop calls changed to top and pop calls (standard stack pop only pops the
element from the stack, but doesn't return a reference); is empty calls
changed to empty; and drop calls changed to pop (equivalent operation)