RFR: 8055006 - Store original value of Min/MaxHeapFreeRatio

[Jesper Wilhelmsson]

Hi,

Please review this change to store the original values of Min- and MaxHeapFreeRatio.

This change also include some makefile changes to make it possible to override 
some variables in the make files. This is needed in preparation for the code 
that will update the Min/MaxHeapFreeRatio later on.

Webrev: http://cr.openjdk.java.net/~jwilhelm/8055006/
Bug: https://bugs.openjdk.java.net/browse/JDK-8055006

Thanks!
/Jesper