message: cmake: check for C++11
diff: @@ -122,6 +122,10 @@ add_library(dronecore STATIC
  ${plugin_source_files}
  )
  +# cmake should check for C++11
  +set_property(TARGET dronecore PROPERTY CXX_STANDARD 11)
  +set_property(TARGET dronecore PROPERTY CXX_STANDARD_REQUIRED ON)
  +
  set_target_properties(dronecore
  PROPERTIES COMPILE_FLAGS ${warnings}
  )
  