function: Use new gi_type_info_extract_ffi_return_value() API
function: Use new gi_type_info_extract_ffi_return_value() API

This allows sharing code between g-i and gjs.

https://bugzilla.gnome.org/show_bug.cgi?id=670249

magcius/gjs,endlessm/gjs,pixunil/cjs,djdeath/gjs,magcius/gjs,djdeath/gjs,mtwebster/cjs,mtwebster/cjs,endlessm/gjs,mtwebster/cjs,mtwebster/cjs,endlessm/gjs,pixunil/cjs,djdeath/gjs,mtwebster/cjs,pixunil/cjs,endlessm/gjs,pixunil/cjs,djdeath/gjs,magcius/gjs,magcius/gjs,djdeath/gjs,magcius/gjs,endlessm/gjs,pixunil/cjs