gtype: mark the inline functions in G_DECLARE_*_TYPE() as UNUSED
clang will warn about static inline functions where gcc will not. Fixes -Werror=unused-function with clang in dependant projects when G_DECLARE_*_TYPE
is not used in headers.
clang will warn about static inline functions where gcc will not. Fixes -Werror=unused-function with clang in dependant projects when G_DECLARE_*_TYPE
is not used in headers.