RFR(s): 8067768: Check for too small values for -Xmx

[Jesper Wilhelmsson]

Looks good.

Slightly related but probably a separate issue is that G1 needs InitialHeapSize 
 >= 2M since it needs one young and one survivor region and the minimum region 
size is 1M...
/Jesper

Den 11/3/16 kl. 15:52, skrev Per Liden:
> Hi,
>
> Summary: The VM needs at least a 2M heap (MaxHeapSize) and at least 1M initial
> heap (InitialHeapSize), but we only check the InitialHeapSize limit during start
> up. This patch adds a check for MaxHeapSize and extends the jtreg heap size test
> to check these limits.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8067768
> Webrev: http://cr.openjdk.java.net/~pliden/8067768/webrev.0/
> Testing: manual, jtreg test/gc/*, jprt in progress
>
> thanks,
> Per
>