[jdk17u-dev] RFR: 8348598: Update Libpng to 1.6.47

[Goetz Lindenmaier]

I had to resolve the makefile.
The same file is edited as in 21, but the
coding looks different in 17.
It differs to head as the make code is in an other file.

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Commit messages:
 - Backport 6b82b42a2116900b2125e03c1ffa0824d6062757

Changes: https://git.openjdk.org/jdk17u-dev/pull/3414/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3414&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348598
  Stats: 4889 lines in 20 files changed: 1905 ins; 2195 del; 789 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/3414.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/3414/head:pull/3414

PR: https://git.openjdk.org/jdk17u-dev/pull/3414