v1.2.13
(04f42ceca40f73e2978b50e93806c2a18c1281fc)

https://github.com/madler/zlib/releases/tag/v1.2.13

We have removed zlib.3.pdf from our local copy, as it is a binary file which is
not needed for our compilation.

We have also cherry-picked into our local copy:

- https://github.com/madler/zlib/commit/e554695638228b846d49657f31eeff0ca4680e8a

  This patch only affects memLevel 9 compression. .NET doesn't currently use this
  memLevel, but we'll take this patch out of an abundance of caution just in case
  we enable this functionality in a future release.

We have also applied the custom patches under the patches/zlib folder.
