When parsing a DW_FORM_ref_addr attribute the CU containing the

When parsing a DW_FORM_ref_addr attribute the CU containing the
abbreviation may not be the current CU.  Thus we need to make sure
that when we read the abbreviation we use the correct CU.

	* dwarf2.c (find_abstract_instance_name): For DW_FORM_ref_addr
	attributes select the CU containing the abbreviation, which may not
	be the current CU.