CMake updated to require clients use C++11

CMakeLists.txt

@@ -208,6 +208,8 @@ target_include_directories(${PROJECT_NAME} PUBLIC
   $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/Inc>
   $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/${PROJECT_NAME}>)
 
+target_compile_features(${PROJECT_NAME} PUBLIC cxx_std_11)
+
 if(WINDOWS_STORE OR BUILD_XAUDIO_WIN10 OR BUILD_XAUDIO_WIN8 OR BUILD_XAUDIO_WIN7)
     target_include_directories(${PROJECT_NAME} PRIVATE Audio)
 endif()