Add missing Unsafe entry points for addAndGet() family

This is a cloned issue so that we have a libs CR and a hotspot CR.

This is missing from JDK-7023898.

The VM support for intrinsifying Unsafe calls in question is there, but no methods is exposed in Unsafe to link against. Should add:

public int getAndAddInt(Object o, long offset, int delta)
public long getAndAddLong(Object o, long offset, long delta)
public long getAndAddLong(Object o, long offset, long delta)
public int getAndSetInt(Object o, long offset, int x)
public long getAndSetLong(Object o, long offset, long x)
public Object getAndSetObject(Object o, long offset, Object x)