[OpenJDK 2D-Dev] RFR: 8254608: Update the classes in the java.awt.color package

[Sergey Bylokhov]

- The spec  for ICC_ProfileRGB.getGamma(int) and ICC_ProfileRGB.getTRC(int) is updated
 - Two additional tests are added to cover some basic specified functionality
 - Some code in these classes was simplified/cleaned
 - Some common code is extracted to the separate methods.

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Commit messages:
 - Update ColorSpace.java
 - Initial fix

Changes: https://git.openjdk.java.net/jdk/pull/612/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=612&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8254608
  Stats: 389 lines in 6 files changed: 284 ins; 77 del; 28 mod
  Patch: https://git.openjdk.java.net/jdk/pull/612.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/612/head:pull/612

PR: https://git.openjdk.java.net/jdk/pull/612