CMake updated to require clients use C++11

CMakeLists.txt

@@ -118,6 +118,8 @@ target_include_directories(${PROJECT_NAME} PUBLIC
   $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/UVAtlas/inc>
   $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
 
+target_compile_features(${PROJECT_NAME} PUBLIC cxx_std_11)
+
 target_include_directories(${PROJECT_NAME} PRIVATE UVAtlas UVAtlas/geodesics UVAtlas/isochart)
 
 if ((${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.16") AND (NOT MINGW))