gmacros: mark functions generated by autoptr macros as unused
gmacros: mark functions generated by autoptr macros as unused

clang will warn with -Wunused-function if the g_autoptr macros are
ever used inside a .c file.  This would break a lot of -Werror builds
with clang.

Mark such functions as explicitly unsed so clang will not warn about
them.

endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib