g_task_set_name() was added in GLib 2.60, so only use it in the
overridden definition of g_task_set_source_tag() if the user has said
that they require GLib ≥ 2.60.
This is a follow up to commit b08bd04a.
Signed-off-by: Philip Withnall email@example.com
This will create a new commit in order to revert the existing changes.