RFR(s): 8212108: SafepointSynchronizer never ending counter (big enough)

[Robbin Ehn]

Hi all, please review.

The counter can loop around, it would mainly be an issue in reading such flight-
recorder recording. I have two upcoming features which uses the fact that it is
always increasing.

CR:
https://bugs.openjdk.java.net/browse/JDK-8212108

Webrev:
http://cr.openjdk.java.net/~rehn/8212108/webrev/

Passes t1-3 and the two updated FR tests.

Thanks Robbin