RFR: 8025856 - Fix typos in the GC code

[Kirk Pepperdine]

> 
> 
> * The logging is now consistent with all collectors.

But not consistent with previous versions. 

> * The logging is now consistent with other tools that use the GC cause, such as j* commands, MBeans and event tracing.

But breaks tools that are in the field
> * The name System is not very informative. It does not really explain what happened. System.gc() is a well know concept for Java users.

What about Runtime.gc(), do we get a different message for that? RMI?

> * The current log statements are present in 7u-releases and will be present the JDK8 release.
> 
> I strongly suggest that we keep the current behavior.

I'm happy to patch...

Regards,
Kirk