Add cdash.org support:

* the dashboard is there: http://my.cdash.org/index.php?project=Eigen
* now you can run the tests from the top build dir
  and submit report like that (from the top build dir):
  ctest -D Experimental
* todo:
 - add some nighlty builds (I'll add a few on my computer)
 - add valgrind memory checks, performances tests, compilation time tests, etc.

CMakeLists.txt

@@ -81,6 +81,7 @@ include_directories(${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_CURRENT_BINARY_DIR})
 add_subdirectory(Eigen)
 
 if(EIGEN_BUILD_TESTS)
+  include(CTest)
   add_subdirectory(test)
 endif(EIGEN_BUILD_TESTS)