Merge libpng version 1.6.58: tag '3061454d980de7d53608f594194cfac722721d2a'

- Strip all unneeded files as per README.fuchsia.
- Resolve modify/delete conflicts by keeping deletions.

Bug: 524829677
Change-Id: Iea319180f6a9673926e65066bdc46c53165f086d
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/libpng/+/1663080
Reviewed-by: Emircan Uysaler <emircan@google.com>