RFR: JDK-8329004 : Update Libpng to 1.6.43 [v2]

[Harshitha Onkar]

> Libpng updated from 1.6.40 to  1.6.43

Harshitha Onkar has updated the pull request incrementally with one additional commit since the last revision:

  added missing 4 lines of header

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/18964/files
  - new: https://git.openjdk.org/jdk/pull/18964/files/229f88f1..f9021883

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18964&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18964&range=00-01

  Stats: 85 lines in 17 files changed: 85 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/18964.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18964/head:pull/18964

PR: https://git.openjdk.org/jdk/pull/18964