[OpenJDK 2D-Dev] RFR: 8130266: Change the mechanism by which JDK loads the platform-specific GraphicsEnvironment class

[Phil Race]

Bug: https://bugs.openjdk.java.net/browse/JDK-8130266
CSR: https://bugs.openjdk.java.net/browse/JDK-
Webrev: http://cr.openjdk.java.net/~prr/8130266/

Please review this fix + the CSR which eliminates the 
java.awt.graphicenv System property.

To replace it we have platform-specific classes which can then more 
easily embed
platform-specific logic. For example, logic in 
java.awt.GraphicsEnvironment was
then moved down into this class. Also isInAquaSession used on Mac was moved
into that class from the Mac Toolkit class.

A reference to the property in J2D Bench - just used to log / document 
the testing environment
was removed along with similar references to two other properties 
removed in earlier fixes.

This has been built + tested on Mac, Linux + Windows in headful mode and 
also
specifying headless via -Djava.awt.headless and by letting it default to 
headless
in an ssh session on Mac + by unsetting the DISPLAY variable on Linux.

-phil.