[Graal upstream] 8201318: Introduce GCThreadLocalData to abstract GC-specific data belonging to a thread

[Per Liden]

Requesting upstreaming of the parts of JDK-8201318 that touched Graal files.

Original bug: https://bugs.openjdk.java.net/browse/JDK-8201318
Final webrev: http://cr.openjdk.java.net/~pliden/8201318/webrev.2/
Commit: http://hg.openjdk.java.net/jdk/hs/rev/93d84f667d12

Thanks!
/Per