hg: jdk8u/jdk8u-dev/jdk: 8220495: Update GIFlib library to the 5.1.8

[dcherepanov at azul.com]

Changeset: 5e4b7ed6e904
Author:    serb
Date:      2019-03-31 16:57 -0700
URL:       http://hg.openjdk.java.net/jdk8u/jdk8u-dev/jdk/rev/5e4b7ed6e904

8220495: Update GIFlib library to the 5.1.8
Reviewed-by: prr

! THIRD_PARTY_README
! src/share/native/sun/awt/giflib/dgif_lib.c
! src/share/native/sun/awt/giflib/gif_hash.h
! src/share/native/sun/awt/giflib/gif_lib.h
! src/share/native/sun/awt/giflib/gif_lib_private.h
! src/share/native/sun/awt/giflib/gifalloc.c
! src/share/native/sun/awt/giflib/openbsd-reallocarray.c