Made lnFunc() method in ContingencyTables public, and adapted classes for J48 splitting criteria to make use of this function (which uses a cache of n*log(n) values for smallish integers n). This yields a very nice speed-up for datasets containing attributes with many distinct numeric values.

git-svn-id: https://svn.cms.waikato.ac.nz/svn/weka/trunk@10054 e0a1b77d-ad91-4216-81b1-defd5f83fa92
Merge remote-tracking branch 'upstream'