Add reference to atk/atkrelationtype.h

Add reference to atk/atkrelationtype.h

* atk/Makefile.am, atk/atk.h: Add reference to atk/atkrelationtype.h

* atk/atkaction.[ch]: Add atk_action_get_localized_name.

* atk/atkobject.[ch]: Add atk_role_get_localized_name,
atk_object_add_relationship and atk_object_remove_relationship
Add new roles ATK_ROLE_HEADER, ATK_ROLE_FOOTER, ATK_ROLE_PARAGRAPH
and ATK_ROLE_RULER

* atk/atkrelation.h: Move definition of AtkRelationType to
atk/relationtype.h

* atk/atkstate.h: Add new state ATK_STATE_MANAGES_DESCENDANTS

* atk/atktext.[ch]: Add text-attributes-changed signal.

* docs/atk-sections.txt, docs/tmpl/atkaction.sgml: Add new functions.

* docs/tmpl/atkobject.sgml: Add new functions and new roles.

* docs/tmpl/atkrelation.sgml: Add new relations

* docs/tmpl/atkstate.sgml: Add new state

* docs/tmpl/atktext.sgml: Add new signal

* tests/testrelation.c: Add tests for new relationship functions.