Require CMake 2.8.12.2 to build CMake itself

This will enable use of features such as ALIAS targets within CMake's
own build.

CMakeLists.txt

@@ -9,7 +9,7 @@
 # implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 # See the License for more information.
 #=============================================================================
-cmake_minimum_required(VERSION 2.8.4 FATAL_ERROR)
+cmake_minimum_required(VERSION 2.8.12.2 FATAL_ERROR)
 if(POLICY CMP0025)
   cmake_policy(SET CMP0025 NEW)
 endif()

Utilities/Doxygen/CMakeLists.txt

@@ -12,7 +12,7 @@
 
 if(NOT CMake_SOURCE_DIR)
   set(CMakeDeveloperReference_STANDALONE 1)
-  cmake_minimum_required(VERSION 2.8.4 FATAL_ERROR)
+  cmake_minimum_required(VERSION 2.8.12.2 FATAL_ERROR)
   get_filename_component(tmp "${CMAKE_CURRENT_SOURCE_DIR}" PATH)
   get_filename_component(CMake_SOURCE_DIR "${tmp}" PATH)
   include(${CMake_SOURCE_DIR}/Modules/CTestUseLaunchers.cmake)

Utilities/Sphinx/CMakeLists.txt

@@ -11,7 +11,7 @@
 #=============================================================================
 if(NOT CMake_SOURCE_DIR)
   set(CMakeHelp_STANDALONE 1)
-  cmake_minimum_required(VERSION 2.8.4 FATAL_ERROR)
+  cmake_minimum_required(VERSION 2.8.12.2 FATAL_ERROR)
   get_filename_component(tmp "${CMAKE_CURRENT_SOURCE_DIR}" PATH)
   get_filename_component(CMake_SOURCE_DIR "${tmp}" PATH)
   include(${CMake_SOURCE_DIR}/Modules/CTestUseLaunchers.cmake)