Review request for JDK-8007273

[Hannes Wallnoefer]

Please review webrev for JDK-8007273 (Creation of ScriptFunctions can be 
refactored):

http://cr.openjdk.java.net/~hannesw/8007273/

This introduces a ScriptFunctionData class that stores everything needed 
to instantiate functions and is stored in a script class's constants array.

It also adds a dedicated ScriptFunction constructors for functions from 
compiled code as opposed to other types of functions such as built-ins. 
This makes code simpler since different types of functions have 
different properties (e.g. built-ins don't have source or token, 
compiled functions don't have to compute arity from signature...).

I also tried various forms of optimization and found the one thing that 
helps is to not adapt method handle signatures into something that can 
be used by used by ScriptFunction.invoke()/.construct() (which mainly 
means boxing the return value to Object) right away in the constructor. 
Instead the method handle is now left unchanged in ScriptFunction and 
only adapted lazily for invoke()/construct(). This seems to improve 
performance in earley-boyer and gbemu by something like 10-20%.

Hannes