Moving to a minimum required CMake version of 3.5.1. This has enabled removal of various version checking logic in the CMake files and moves to a more recent CMake version.
Since Ubuntu 14.04 is now out of LTS, the oldest LTS release of Ubuntu is 16.04 which includes CMake 3.5.1. CentOS 6, which is "end of life" in Nov 2020 includes the cmake3 package for version 3.6.1. Debian Jessie includes only CMake 3.0.2 as it's packaged version but Jessie reaches the end of LTS and is "end of life" at the end of June 2020. Debian Stretch will then become the oldest supported LTS release and this includes CMake 3.7.2.
Also restructured third party Zlib handling for Win32 to remove confusion and support upcoming Windows changes for third party boost builds. At present the
THIRDPARTY_LIBRARY macro is called with the library type
WIN32 because Windows needs to use the .lib file for linking at build time on Windows, even when doing dynamic linking. It will use the associated
.dll file at runtime. This is changed to call the macro with
SHARED and the check for
WIN32 and use of the
STATIC type even for dynamic linking on Windows is handled within the macro itself to provide a more general solution.