All exceptional conditions in compilation units take the form of
  THING_error(), which is GL-style copy and clear and return the copy,
  so reset doesn't need to happen in main unit


* All exceptional conditions in compilation units take the form of THING_error(), which is GL-style copy and clear and return the copy, so reset doesn't need to happen in main unit

* Factor out memory_write_block, us from write_ROM_image



Add note about memory write
Add note about memory write
