RFR: 8009763 Add WB test for String.intern()

[Leonid Mesnik]

Hi
I've added a small test which:
1) creates java string and intern it
2) verify that it presents in StringTable
3) clear reference and call fullGC
4) verify that there is no such string in StringTable

Here is webrev:
http://cr.openjdk.java.net/~mgerdin/lmesnik/webrev.0/

Tested locally and by JPRT

-- 
Leonid Mesnik
JVM SQE