CMake deprecation warning with versions below 3.5.0

[hirrolot]

While building Datatype99, the following error is produced by CMake:

CMake Deprecation Warning at build/_deps/metalang99-src/CMakeLists.txt:1 (cmake_minimum_required):
  Compatibility with CMake < 3.5 will be removed from a future version of
  CMake.

  Update the VERSION argument <min> value or use a ...<max> suffix to tell
  CMake that the project does not need compatibility with older versions.

The solution would be to upgrade the CMake minimum required version to 3.5.0 as follows:

cmake_minimum_required(VERSION 3.5.0)