Implement json_node_get_parent()
Implement json_node_get_parent()

It seems that the parent accessor fell through. This commit implements
the declared json_node_get_parent() function.

ebassi/json-glib,GNOME/json-glib,oerdnj/json-glib,robtaylor/json-glib-gvariant,Distrotech/json-glib,robtaylor/json-glib-gvariant,frida/json-glib,brauliobo/json-glib,ebassi/json-glib,oerdnj/json-glib,brauliobo/json-glib,oerdnj/json-glib,Distrotech/json-glib,oerdnj/json-glib,brauliobo/json-glib,Distrotech/json-glib,ebassi/json-glib,frida/json-glib,GNOME/json-glib