<AWT Dev> [10] Review Request: 8186474 WColor class is superseded by the SystemColor and should be removed

[Sergey Bylokhov]

Hello,
Please review the simple cleanup for jdk10.

Long time ago AWT used WColor class to access the native colors, but since then we integrated a public API via SystemColor class.
So WColor class became obsolete and can be removed.

Bug: https://bugs.openjdk.java.net/browse/JDK-8186474
Webrev can be found at: http://cr.openjdk.java.net/~serb/8186474/webrev.01