Shared Library Changes for Release 2.1.4

Shared library libddcutil is backwardly compatible with the one in ddcutil 2.0.0. The SONAME is unchanged as The released library file is

Previously deprecated API function ddca_create_display_ref() (an alternative name for ddca_get_display_ref()) was removed in release 2.0.0. It has been restored, allowing some existing programs in Debian to use libddutil unchanged.