[9] RFR (S) 8146436: Add -XX:+UseAggressiveHeapShrink option

[Chris Plummer]

Hello,

Please review the following for adding the -XX UseAggressiveHeapShrink 
option. When turned on, it tells the GC to reduce the heap size to the 
new target size immediately after a full GC rather than doing it 
progressively over 4 GCs.

Webrev: http://cr.openjdk.java.net/~cjplummer/8146436/webrev.02/
Bug: https://bugs.openjdk.java.net/browse/JDK-8146436

Testing:
   -JPRT with '-testset hotspot'
   -JPRT with '-testset hotspot -vmflags "-XX:+UseAggressiveHeapShrink"'
   -added new TestMaxMinHeapFreeRatioFlags.java test

thanks,

Chris