<AWT Dev> [13] Review Request: 8220320 Remove unused old code in GraphicsEnvironment on unix

[Sergey Bylokhov]

Hello.
Please review small fix for JDK 13.

Bug: https://bugs.openjdk.java.net/browse/JDK-8220320
Fix: http://cr.openjdk.java.net/~serb/8220320/webrev.00

  - The X11GraphicsDevice.initID() can be removed, because it is unused and its native implementation was dropped already.
  - The code related to #ifdef NETSCAPE can be dropped
  - the null checks in Java_sun_awt_X11GraphicsConfig_initIDs() after "CHECK_NULL()" are redundant

-- 
Best regards, Sergey.