Do not add support for its subtypes, since all their constructors return
GParamSpec*, and g_param_spec_unref() takes a GParamSpec* rather than a
gpointer — adding G_DEFINE_AUTOPTR_CLEANUP_FUNC() for subtypes of
GParamSpec results in compiler warnings about mismatched parameter
types (GParamSpecBoolean* vs GParamSpec*, for example).
Signed-off-by: Philip Withnall <withnall@endlessm.com>
https://bugzilla.gnome.org/show_bug.cgi?id=796139