**Motivation**
ZGC currently modify mark-bitmap by a conditional atomic operation (cmpxchg). This way is not optimal, which will retry the loop when cmpxchg fails.

First, This patch-set add an new unconditional atomic operation: Atomic::fetch_and_or, which is implemented in different ways for different CPU architectures:

* Exclusive access: non-nested loop

```
retry:
  ll old_val, addr
  or new_val, old_val, set_val
  sc new_val, addr
  beq retry
```

* Atomic access: one instruction

```
ldset old_val, set_val, addr
```

* Generic: fallback to cmpxchg or use c++ __atomic_fetch_or

**Testing**
* jtreg tests
* benchmark tests

Assigned to wangrui.

Thanks,
Leslie ZHai