Merge #69: Fix CMake minimum required version

6902bfd Fix CMake minimum required version (Hennadii Stepanov)

Pull request description:

  The "C++17" value of the [`CXX_STANDARD`](https://cmake.org/cmake/help/latest/prop_tgt/CXX_STANDARD.html) target property, which was introduced in #25, is available in CMake 3.8 and newer.

  Tested with old CMake versions available [here](https://cmake.org/files/).

ACKs for top commit:
  ryanofsky:
    Code review ACK 6902bfd. Thanks for the PR!

Tree-SHA512: 5ebb0f50c4e8799903f4ce54e6fcf66616d4d4b7b85b8789fc72728f009791bb844453c1ff285a4b06e6fb6951f168f5656f7018c80bda5807faa6aa3703342d

CMakeLists.txt

@@ -2,7 +2,7 @@
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-cmake_minimum_required(VERSION 3.0)
+cmake_minimum_required(VERSION 3.8)
 project("Libmultiprocess" CXX)
 include(CMakePushCheckState)
 include(CheckCXXSourceCompiles)