Log Message:
optipng: updated to 0.7.7

0.7.7:
* Upgraded libpng to version 1.6.34.
* Upgraded zlib to version 1.2.11-optipng.
* Upgraded minitiff to version 0.2.
!! Fixed a buffer overflow vulnerability in the GIF decoder.
!! Fixed an integer overflow vulnerability in the TIFF decoder.
! Fixed the build on macOS High Sierra.
! Fixed the build on DJGPP.
* Disallowed out-of-bounds values in rangeset options.