RFR [9] 8071472: Add field setter API for setting final fields in readObject

[Chris Hegarty]

Here is an updated version of the FieldSetter API, with all comments to 
date incorporated.

http://cr.openjdk.java.net/~chegar/8071472/02/specdiff/overview-summary.html

Final spec comments welcome, after which I intend to submit a CCC request.

-Chris.