Review request for JDK-8013208 Octane performance regression

[Jim Laskey]

http://cr.openjdk.java.net/~jlaskey/8013208/webrev.01/index.html

convertKey was called every time an indexed getter was invoked, instead of 
conditionally.  Reworked the code to be conditionally calledl, also optimizing 
for Integer (boxed) values (very frequent) and cases when key is not an index.