[CMake] Drop setting of CMP0054 policy to OLD behavior

This does not seem to be necessary. Eventually CMake will remove
the old behavior, so it's better to switch to the new behavior.
See "cmake --help-policy CMP0054" for information on this policy.

CMakeLists.txt

@@ -9,11 +9,6 @@ set( CMAKE_MODULE_PATH
  ${PROJECT_SOURCE_DIR}/src
  ${PROJECT_SOURCE_DIR}/cmake )
 
-if(NOT (CMAKE_VERSION VERSION_LESS "3.1"))
-  cmake_policy(SET CMP0054 OLD)
-endif()
-
-
 #-------------------------------------------------------------------------------
 # A 'plugins' phony target to simplify building build-tree binaries.
 # Plugins are responsible for adding themselves to this target, where