RFR: Rename enter/exit_critical to pin_object

[Aleksey Shipilev]

On 10/05/2016 09:45 AM, Roman Kennke wrote:
> Christine suggested to rename enter_critical() and exit_critical() in
> CollectedHeap (and related) to pin_object() and unpin_object(). I agree
> that this is a more useful name and this change implements that:
> 
> http://cr.openjdk.java.net/~rkennke/rename-critical/webrev.01/
> 
> Ok?

OK. Would not mind have a little comment in collectedHeap.hpp.

Thanks,
-Aleksey