[Patch] Support GraalVM in CompilerHints

[Eric Caspole]

Hi everybody,
Could I get reviews and a sponsor for this small patch to support the 
OpenJDK-based GraalVM[1] and eliminate a warning with the compiler hints.

http://cr.openjdk.java.net/~ecaspole/jmh-graalvm/webrev/

Thanks,
Eric

[1] http://www.graalvm.org/