Update CMake minimum required version

[AnHeuermann]

CMake 4 deprecates compatbility with CMake < 3.10 which results in a warning like:

CMake Deprecation Warning at DCPLib/CMakeLists.txt:1 (cmake_minimum_required):Compatibility with CMake < 3.10 will be removed from a future version of
CMake.

Update the VERSION argument <min> value.  Or, use the <min>...<max> syntax
to tell CMake that the project requires at least <min> but has been updated
to work with policies introduced by <max> or earlier.

To fix this update

cmake_minimum_required(VERSION 3.5)

to a more recent version.