RFR: 8223822: Add gc IDs in the log of gc verification

[Thomas Schatzl]

Hi,

On Tue, 2019-05-14 at 15:35 +0800, Jie Fu wrote:
> Hi all,
> 
> JBS: https://bugs.openjdk.java.net/browse/JDK-8223822
> 
> Please review the following patch which improves the readability of
> gc verification log.
> The change is helpful for gc analysis and debugging.
> -----------------------------------
> diff -r 6a60270af76b src/hotspot/share/logging/logPrefix.hpp
> --- a/src/hotspot/share/logging/logPrefix.hpp   Mon May 13 20:45:03
> 2019 

looks good.

Thomas