Merge topic 'update-zlib'

87b304f649 zlib: Add CMakeLists.txt for build within CMake
b0d97aeea5 zlib: Use unistd.h on all non-Windows platforms
19881cbdec zlib: Suppress some MSVC warnings
0d201ad25b zlib: Add initialization to satisfy valgrind
512c1f8f75 zlib: Fix typo in comment
2be780ba5b Merge branch 'upstream-zlib' into update-zlib
40a17e3f5e zlib: add script to import zlib 1.2.3 from upstream
fc22ac115e zlib: Drop old sources to make room for a fresh import
...

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: buildbot <buildbot@kitware.com>
Merge-request: !7300