[jdk8u-dev] RFR: 8328999: Update GIFlib to 5.2.2 [v2]

[Andrew John Hughes]

> This updates the in-tree giflib to 5.2.2. The actual code changes are a clean backport, but the license file changes needed adapting from the `giflib.md` file in 11u and later to the `THIRD_PARTY_README` file in 8u (now only one copy following [JDK-8338144](https://bugs.openjdk.org/browse/JDK-8338144))
> 
> 8u is also missing [JDK-8225487](https://bugs.openjdk.org/browse/JDK-8225487) which I've included as part of this patch. This updates the license to credit `openbsd-reallocarray.c` and is updated further by 8238999. I also included changes made by the 5.2.1 update which were missed because 8225487 was missing.
> 
> In `gif_lib.h`, I have restored the workaround for a missing `stdbool.h` on Windows only. This is needed to build on Visual Studio 2010.
> 
> The `giflib.md` changes include some odd changes, replacing the giflib VCS URL with just `tree/README`. I've raised [8339271](https://bugs.openjdk.org/browse/JDK-8339271) to correct this and will look at backporting that as a follow-up.

Andrew John Hughes has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Restore local modifications on Windows to work around missing stdbool.h on VS2010
 - Merge remote-tracking branch 'dev/master' into JDK-8328999
 - Backport bc8aeb6496b7e86d1f616d4c1b7c26f172c1dd8a

-------------

Changes:
  - all: https://git.openjdk.org/jdk8u-dev/pull/571/files
  - new: https://git.openjdk.org/jdk8u-dev/pull/571/files/d96b50f0..40ab6a93

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=571&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=571&range=00-01

  Stats: 4232 lines in 71 files changed: 3442 ins; 371 del; 419 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/571.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev.git pull/571/head:pull/571

PR: https://git.openjdk.org/jdk8u-dev/pull/571