RFR: 8008917 CMS: Concurrent mode failure tracing event

[Kevin Walls]

Hi,

I'd like some reviews on this CMS Concurrent Mode Failure event:

http://cr.openjdk.java.net/~kevinw/8008917/hotspot/

The event doesn't actually carry any new information, but it is a 
warning we need to capture.

This is against hsx24, I'll prepare the same, or reviewed, changes 
against very latest hotspot also.

Thanks
Kevin