RFR: 8031639: make dependency management (mostly) ci independent

[Doug Simon]

Hi all,

I would like to request a review for a change to the Dependencies class such that it can be used to register assumptions based on either ci* values or raw values. The motivation is support compilers (such as Graal) that don't use the ci interface. 

jbs:    https://bugs.openjdk.java.net/browse/JDK-8031639
webrev: http://cr.openjdk.java.net/~dnsimon/JDK-8031639/

-Doug