8384902: Update GIFlib to 6.1.3

[vieiro]

Backport of JDK-8384902 from JDK-11.

There's a slight difference from JDK-11 in the way SavedImage *correct_saved_images; is declared in dgif_lib.c/DGifDecreaseImageCounter, introduced when backporting JDK-8379256 to JDK8.

Tested on RH8/gcc 8.5.0 with jdk/test/java/awt/SplashScreen tests, passing:

TEST RESULT: Passed. Execution successful
--------------------------------------------------
Test results: passed: 1

---

• I confirm that I make this contribution in accordance with the OpenJDK Interim AI Policy.

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• JDK-8384902 needs maintainer approval
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8384902: Update GIFlib to 6.1.3 (Bug - P3)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk8u-dev.git pull/827/head:pull/827
$ git checkout pull/827

Update a local copy of the PR:
$ git checkout pull/827
$ git pull https://git.openjdk.org/jdk8u-dev.git pull/827/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 827

View PR using the GUI difftool:
$ git pr show -t 827

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk8u-dev/pull/827.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back avieiro! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

This backport pull request has now been updated with issue from the original commit.

[mlbridge]

Webrevs

• 00: Full (de232c64)