Fixed cmake warnings.

Author: redboltz

CMakeLists.txt

@@ -1,6 +1,12 @@
-CMAKE_MINIMUM_REQUIRED (VERSION 3.1 FATAL_ERROR)
-
-CMAKE_POLICY (SET CMP0054 NEW)
+if(${CMAKE_VERSION} VERSION_GREATER "3.4")
+    CMAKE_MINIMUM_REQUIRED (VERSION 3.5)
+else()
+    CMAKE_MINIMUM_REQUIRED (VERSION 2.8.12)
+    IF ((CMAKE_VERSION VERSION_GREATER 3.1) OR
+        (CMAKE_VERSION VERSION_EQUAL 3.1))
+        CMAKE_POLICY(SET CMP0054 NEW)
+    ENDIF ()
+endif()
 
 PROJECT (msgpack-cxx LANGUAGES CXX)
 
@@ -67,6 +73,10 @@ IF (MSGPACK_32BIT)
 ENDIF ()
 
 IF (MSGPACK_USE_BOOST)
+    IF ((CMAKE_VERSION VERSION_GREATER 3.0) OR
+        (CMAKE_VERSION VERSION_EQUAL 3.0))
+        CMAKE_POLICY(SET CMP0167 NEW)
+    ENDIF ()
     SET (Boost_USE_MULTITHREADED ON)
 
     IF (MSGPACK_USE_STATIC_BOOST)