message: hot restart: bump version
  The stats change in does not
  actually change the size of the shared memory region due to compiler
  alignment (at least on gcc 4.9). This will force a shared memory region
  version bump.
diff: @@ -14,7 +14,7 @@ namespace Server {
  // Increment this whenever there is a shared memory / RPC change that will prevent a hot restart
  // from working. Operations code can then cope with this and do a full restart.
  -const uint64_t SharedMemory::VERSION = 3;
  +const uint64_t SharedMemory::VERSION = 4;
  SharedMemory& SharedMemory::initialize(Options& options) {
  int flags = O_RDWR;
  