RFR(M): 8076188 Optimize arraycopy out for non escaping destination

[Roland Westrelin]

http://cr.openjdk.java.net/~roland/8076188/webrev.00/

This patch tries to eliminate ArrayCopyNodes (for instance clones, array clones, arraycopy and copyOf) when the destination of the copy doesn’t escape:

- during escape analysis, ArrayCopyNodes don’t cause the destination of the copy to be marked as escaping anymore
- a load to the destination of a copy may be replaced by a load from the source during IGVN
- during macro expansion, ArrayCopyNodes don’t stop allocation from being eliminated and can themselves be eliminated 

Roland.