Update stdpp

See merge request iris/iris!650

let users access iFrame helper tactics

See merge request iris/iris!648

Make Iris compatible with name mangling

Closes #343

See merge request iris/iris!647

New Camera dyn_reservation_map and generalize namespace_map → reservation_map

See merge request iris/iris!646

Use ghost_map in proph_map and gen_heap

See merge request iris/iris!645

Flexible number of logical steps per physical step

See merge request iris/iris!595

* Rename ghost_map_elem_elem_frac_ne → ghost_map_elem_frac_ne,
  ghost_map_elem_elem_ne → ghost_map_elem_ne.
* Make ghost_map_elem_persist work for arbitrary `dfrac`.
* Add ghost_map_insert_persist.

add ghost_map library

Closes #358

See merge request iris/iris!562

Makes it possible to use several logical steps for one logical steps, in a way which can be controlled by ghost state.