[foreign-abi] RFR 8228486: Add ABI-specific layout constants

[Maurizio Cimadamore]

Hi,
the recent push for JDK-8228447, as expected, broke the foreign-abi 
branch, since that branch depended on the ValueLayout::isIntegral accessor.

This patch replaces that logic with the custom layout annotation logic 
discussed in [1]:

http://cr.openjdk.java.net/~mcimadamore/panama/8228486/

This patch makes the following changes:

* introduces three set of annotated layout constants, one for supported ABI
* the annotations point directly at the ABI-specific argument classes
* I've consolidated ArgumentClass a bit, so that now there's a common, 
ABI-agnostic super-interface with some general predicates
* AddressLayout has been removed (we can just look for 
argumentClass::isPointer)
* the tests have been tweaked to use the new ABI-specific constants; 
since the test has to work across platforms, all ABI test use a new 
interface which imports the 'right' set of constants

While the patch might be a bit raw (I've only tested on Linux x64), I 
like where this is going.

Maurizio