Build: Set CMP0053 to NEW.

If this policy is WARN, then the ReplaceVariableInString is executed with both
the new algorithm and the OLD slow algorithm.  The NEW algorithm should be used
wherever it works.

CMakeLists.txt

@@ -13,6 +13,9 @@ cmake_minimum_required(VERSION 2.8.4 FATAL_ERROR)
 if(POLICY CMP0025)
   cmake_policy(SET CMP0025 NEW)
 endif()
+if(POLICY CMP0053)
+  cmake_policy(SET CMP0053 NEW)
+endif()
 project(CMake)
 
 if(CMAKE_BOOTSTRAP)