MNK-5379 : allow more heap for IBM J9

git-svn-id: http://svn.terracotta.org/svn/ehcache@7909 b9324663-ca0f-0410-8574-be9b3887307d
MNK-5379 : merge 7909 from trunk

git-svn-id: http://svn.terracotta.org/svn/ehcache@7910 b9324663-ca0f-0410-8574-be9b3887307d
MNK-5379 : merge 7909 from trunk

git-svn-id: http://svn.terracotta.org/svn/ehcache@7911 b9324663-ca0f-0410-8574-be9b3887307d