RFR: 8186248 - Allow more flexibility in selecting Heap % of available RAM

[Bob Vandette]

Please review this simple two line fix which allows more flexibility in selecting the % of system RAM 
to be used by the Heap.  This just changes two int variables to doubles.

RFE:
https://bugs.openjdk.java.net/browse/JDK-8186248 <https://bugs.openjdk.java.net/browse/JDK-8186248>

Webrev:
http://cr.openjdk.java.net/~bobv/8186248 <http://cr.openjdk.java.net/~bobv/8186248>

Bob.