Add -Wextra to compiler flags.
Add -Wextra to compiler flags.

geographiclib/geographiclib,Sciumo/GeographicLib,Sciumo/GeographicLib,geographiclib/geographiclib,geographiclib/geographiclib,Sciumo/GeographicLib,Sciumo/GeographicLib,Sciumo/GeographicLib,geographiclib/geographiclib,Sciumo/GeographicLib,Sciumo/GeographicLib,Sciumo/GeographicLib