message: disable compilation of test catch when tests turned off
  a side effect is that this allows compilation under visstudio2013
  where noexcept is not available.
diff: @@ -197,7 +197,9 @@ else()
  ## Build Test Apps ##
  + if (OSPRAY_ENABLE_TESTS)
  add_library(ospray_test_main STATIC testing/catch_main.cpp)
  + endif()
  # containers/AlignedVector
  ospray_create_test(test_AlignedVector
  