emitter: try_get_storage -> get_storage. More cruft removal.
emitter: try_get_storage -> get_storage. More cruft removal.

Every call of try_get_storage was having to check for failure and then to see if
it needed to raise nomem. No more. get_storage will now never return a NULL
storage, and raise nomem if that's needed. This removes a bunch of duplicate
potential-raising code from a lot of different parts of the emitter. Good
riddance.

boardwalk/lily,crasm/lily,crasm/lily,boardwalk/lily,crasm/lily