<AWT Dev> RFR: 8242559 Clean the "libawt_xawt" library from code for headless mode

Mon Apr 27 13:01:57 UTC 2020

Hello.
Please review the fix for jdk/client.

Bug: https://bugs.openjdk.java.net/browse/JDK-8242559
Fix: http://cr.openjdk.java.net/~serb/8242559/webrev.00

This bug extracted from JDK-8240290[1]

The libawt_xawt.so library is used by the headful toolkit, but it still
uses some code related to the headless mode, which could be deleted.

In the fix the HEADLESS related code was removed, to prove that we did not
build this library in HEADLESS mode, I added "#error This " to the library files.

[1] https://bugs.openjdk.java.net/browse/JDK-8240290

-- 
Best regards, Sergey.