hg: valhalla/valhalla: Copy of langtools combo testing lib, with set combinations support added

[david.simms at oracle.com]

Changeset: 07d54d244d0f
Author:    dsimms
Date:      2017-06-15 15:06 +0200
URL:       http://hg.openjdk.java.net/valhalla/valhalla/rev/07d54d244d0f

Copy of langtools combo testing lib, with set combinations support added

+ test/lib/jdk/test/lib/combo/ComboInstance.java
+ test/lib/jdk/test/lib/combo/ComboParameter.java
+ test/lib/jdk/test/lib/combo/ComboTask.java
+ test/lib/jdk/test/lib/combo/ComboTestHelper.java
+ test/lib/jdk/test/lib/combo/ReusableContext.java