Revert "Silence verbose cmake policy warnings on Windows"

This causes an error since those policies aren't known by
2.8.12, so better seeing those warnings on Windows for now.

This reverts commit 4441d3b342073bed9d2eba1f8de86db1de7611d2.

CMakeLists.txt

@@ -1,7 +1,5 @@
 cmake_minimum_required(VERSION 2.6)
-cmake_policy(VERSION 2.8.12)
-cmake_policy(SET CMP0043 NEW) # For VERSION < 3.3
-cmake_policy(SET CMP0058 NEW) # For VERSION < 3.3
+cmake_policy(VERSION 2.8.0)
 
 project(client)