<AWT Dev> [14] Review Request: 8230597 Update GIFlib library to the 5.2.1

[Sergey Bylokhov]

Hello.
Please review the fix for JDK 14.

Bug: https://bugs.openjdk.java.net/browse/JDK-8230597
Fix: http://cr.openjdk.java.net/~serb/8230597/webrev.00

The giflib was updated from 5.1.8 to 5.2.1.

Some "JDK modifications" were dropped because the upstream code was fixed.

Mach5 is green.

-- 
Best regards, Sergey.