"JEP Two" draft updated

[John Rose]

Igor’s work on persisting method-profile data, in the AOT cache,
is coming along.  So I took another look at our draft JEP for that
work.  Since the JEP boils down to a single flag, turned on by,
default, there was no need for a long exposition of the ins and
outs of JVM dynamism theory and practice.  So I made it short
and sweet.  See what you think:

https://bugs.openjdk.org/browse/JDK-8325147

— John