JDK 9 RFR of 8042478: Include Mersenne primes in BigInteger primality testing

[Brian Burkhalter]

Hello,

This follows from a prior discussion thread http://mail.openjdk.java.net/pipermail/core-libs-dev/2014-May/026771.html.

Issue:	https://bugs.openjdk.java.net/browse/JDK-8042478
Patch:	http://cr.openjdk.java.net/~bpb/8042478/webrev.00/

Adds a test of the first 19 Mersenne primes. The remainder of the exponent list is commented out as it takes too long to run. The value 19 appears to give a reasonable execution time. The largest Mersenne prime tested is 285542542228902608580607.

Thanks,

Brian