RFR 8218615 [lworld] C1 intrinsic support for System.arraycopy

[Ioi Lam]

https://bugs.openjdk.java.net/browse/JDK-8218615
http://cr.openjdk.java.net/~iklam/valhalla/8218615-c1-arraycopy-intrinsics.v01/

+ If at compile time, we know that at least one of src or dst is a 
flattened array,
   always take the slow path (normal method invocation of System.arraycopy).

+ If src and/or dst may be a flattened array, at runtime, we check if 
they are
   actually flattened. If so, take the slow path.

Note: unlike C2, C1 never deoptimizes arraycopy. I updated TestArrays.java
accordingly.

Thanks
- Ioi