RFR(M): 6700100: optimize inline_native_clone() for small objects with exact klass

[Roland Westrelin]

http://cr.openjdk.java.net/~roland/6700100/webrev.00/

Converts ArrayCopy nodes for small instance clones to series of loads/stores + a little bit of cleanup.

Small array clones & copies as loads/stores are coming next in another change.

Roland.