ENH: min cmake required 2.6

Testing/CMakeLists.txt

@@ -15,7 +15,7 @@ IF(OTB_BINARY_DIR)
   ADD_SUBDIRECTORY(Utilities)
 ELSE(OTB_BINARY_DIR)
   # We are building as a stand-alone project.
-  CMAKE_MINIMUM_REQUIRED(VERSION 2.4)
+  CMAKE_MINIMUM_REQUIRED(VERSION 2.6)
   SET(LIBRARY_OUTPUT_PATH ${OTBTesting_BINARY_DIR}/bin CACHE PATH "Single output directory for building all libraries.")
   SET(EXECUTABLE_OUTPUT_PATH ${OTBTesting_BINARY_DIR}/bin CACHE PATH "Single output directory for building all executables.")
   MARK_AS_ADVANCED(LIBRARY_OUTPUT_PATH EXECUTABLE_OUTPUT_PATH)