allocateLocal(): bump the block count on the step, not the global
alloc_blocks count.
// full: allocate a fresh block (we can't fail here).
ACQUIRE_SM_LOCK;
bd = allocBlock();
// full: allocate a fresh block (we can't fail here).
ACQUIRE_SM_LOCK;
bd = allocBlock();
+ reg->rNursery->n_blocks++;
RELEASE_SM_LOCK;
bd->gen_no = 0;
bd->step = g0s0;
RELEASE_SM_LOCK;
bd->gen_no = 0;
bd->step = g0s0;