Bumped ralph version: speculation on readers had been broken.  See
associated ralph commit messages.
Large refactoring for speculation.  New model will allow events to
take read locks on internal switch elements.  This is because we need
to allow speculation when a read event finishes.  Next commit will add
read locks to ralph source.
Added read locks for basic switch accesses.  These allow internal switch guard to catch read commits on ftable and ftable_delta and speculate on top of them.