Find out how the start address of the loaded object file is set in the simulator

[Reuben Thomas]

For Bee, it's loaded at address 0. Yet moxie's simulator, from which Bee's is derived, uses low memory for a copy of argv, so presumably enforces a different load address. It would be useful to do something similar in Bee so we only have one memory area for the stacks and argv so that memory translation can be fast.