[jdk17u-dev] RFR: 8305815: Update Libpng to 1.6.39

[Goetz Lindenmaier]

I backport this for parity with 17.0.9-oracle.

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

Commit messages:
 - Backport 14874779eeb9a279479c5aaddb40c056780d6152

Changes: https://git.openjdk.org/jdk17u-dev/pull/1464/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1464&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305815
  Stats: 101 lines in 10 files changed: 15 ins; 1 del; 85 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1464.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1464/head:pull/1464

PR: https://git.openjdk.org/jdk17u-dev/pull/1464