RFR (8u) Changed claim count to jint

[Zhengyu Gu]

Changed claim counter from jlong to jint to avoid nasty 
Atomic::add(jlong, jlong*) bug, which returns old value, instead of 
updated value (as comment stated).

It is unlikely the number of regions can overflow max int, and avoid 
using jlong, in case of fixing it in future release, that can break us 
again.

http://cr.openjdk.java.net/~zgu/shenandoah/verf_count_jint/webrev.00/


Test:

   hotspot_gc_shenandoah fastdebug in VBox where the problem was discovered.


Thanks,

-Zhengyu