RFR: Add diagnostic flag to disable inline assembler write barrier

[Aleksey Shipilev]

On 08/31/2017 07:15 PM, Roman Kennke wrote:
> This patch adds a (diagnostic) flag to disable the inline assembler
> write barrier code. This should enable to measure the performance impact
> of it.
> 
> http://cr.openjdk.java.net/~rkennke/disableasmwb/webrev.00/

We should avoid "Disable" options that yield double negations like -XX:-ShenandoahDisableAsmWB.
Otherwise seems fine.

Thanks,
-Aleksey