cmake warnings

Under cmake 3.2.2 running cmake produces a huge warning:

CMake Warning (dev) at CMakeLists.txt:56 (PROJECT): Policy CMP0048 is not set: project() command manages VERSION variables. Run "cmake --help-policy CMP0048" for policy details. Use the cmake_policy command to set the policy and suppress this warning.

The following variable(s) would be set to empty:

PROJECT_VERSION
PROJECT_VERSION_MAJOR

This warning is for project developers. Use -Wno-dev to suppress it.