RFR: 8328999: Update GIFlib to 5.2.2

[Alisen Chung]

Updating giflib, clientlibs tests are green on all platforms

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Commit messages:
 - update md
 - revert tab spacing to spaces
 - init commit

Changes: https://git.openjdk.org/jdk/pull/18985/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18985&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8328999
  Stats: 846 lines in 8 files changed: 179 ins; 105 del; 562 mod
  Patch: https://git.openjdk.org/jdk/pull/18985.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18985/head:pull/18985

PR: https://git.openjdk.org/jdk/pull/18985