Update CMAKE_MINIMUM_REQUIRED VERSION to 2.8.12
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
# IN THE SOFTWARE.
-CMAKE_MINIMUM_REQUIRED(VERSION 2.8.11)
+CMAKE_MINIMUM_REQUIRED(VERSION 2.8.12)
CMAKE_POLICY(SET CMP0003 NEW)
PROJECT(h2o)
