Default the SelfTest project to C++11

Unlike the previous approach, this will still obey
`-DCMAKE_CXX_STANDARD=X` properly.

projects/CMakeLists.txt

@@ -308,6 +308,32 @@ include(CTest)
 add_executable(SelfTest ${TEST_SOURCES} ${IMPL_SOURCES} ${REPORTER_SOURCES} ${SURROGATE_SOURCES} ${HEADERS})
 target_include_directories(SelfTest PRIVATE ${HEADER_DIR})
 
+# It took CMake until 3.8 to abandon the doomed approach of enumerating
+# required features so we just list C++11 features to support older ones.
+target_compile_features(SelfTest
+  PRIVATE
+    cxx_alignas
+    cxx_alignof
+    cxx_attributes
+    cxx_auto_type
+    cxx_constexpr
+    cxx_defaulted_functions
+    cxx_deleted_functions
+    cxx_final
+    cxx_lambdas
+    cxx_noexcept
+    cxx_override
+    cxx_range_for
+    cxx_rvalue_references
+    cxx_static_assert
+    cxx_strong_enums
+    cxx_trailing_return_types
+    cxx_unicode_literals
+    cxx_user_literals
+    cxx_variadic_macros
+)
+
+
 if (CATCH_ENABLE_COVERAGE)
     set(ENABLE_COVERAGE ON CACHE BOOL "Enable coverage build." FORCE)
     find_package(codecov)