RFR: 8243996: Remove hardcoded field offsets from HotSpot

[Erik Österlund]

Hi,

Let's remove hardcoded field offsets. Main trick to get this done is to 
split interpreter initialization
into two parts: 1. reserve the interpreter memory, 2. generate the 
interpreter. This allows reserving
it before loading methods (which generates i2c adapters that assert 
things are "in the interpreter",
requiring knowledge about its address range), and then load the methods, 
and then generate the interpreter.
This moving of interpreter code generation until after methods have been 
loaded allows offsets to be
looked up, needed by code generation. That way, we no longer need to 
hardcode field offsets, which
makes it less annoying to change the field layout code in the future.

Thanks to Coleen for pre-reviewing this.

Bug:
https://bugs.openjdk.java.net/browse/JDK-8243996

Webrev:
http://cr.openjdk.java.net/~eosterlund/8243996/webrev.01/

Thanks,
/Erik