Review request for JDK-8026016: too many relinks dominate avatar.js http benchmark

[Hannes Wallnoefer]

Please review JDK-8026016: too many relinks dominate avatar.js http 
benchmark.

http://cr.openjdk.java.net/~hannesw/8026016/webrev.02/
Apart from the fix to let callsites for non-existant properties go 
megamorphic (while preserving noSuchMethod functionality) this also 
removes some minor inefficiencies in ScriptObject. set() methods used to 
check key for array index twice, and has*() methods unnecessarily 
created an FindProperty object.

Thanks,
Hannes