* a-exexpr.adb (Others_Value, All_Others_Value): New variables, the
	address of which may be used to represent "others" and "all others"
	choices in exception tables, instead of the current harcoded
	(void *)0 and (void *)1.
	(Setup_Exception): Do nothing in the GNAT SJLJ case.

	* gigi.h (others_decl, all_others_decl): New decls representing the
	new Others_Value and All_Others_Value objects.
	(struct attrib): Rename "arg" component as "args", since GCC expects a
	list of arguments in there.

	* raise.c (GNAT_OTHERS, GNAT_ALL_OTHERS): Are now the address of the
	corresponding objects exported by a-exexpr, instead of hardcoded dummy
	addresses.

	* trans.c (Exception_Handler_to_gnu_zcx): Use the address of
	others_decl and all_others_decl instead of hardcoded dummy addresses
	to represent "others" and "all others" choices, which is cleaner and
	more flexible with respect to the possible eh pointer encoding policies.

	* utils.c (init_gigi_decls): Initialize others_decl and all_others_decl.
	(process_attributes): Account for the naming change of the "args"
	attribute list entry component.

	* decl.c (build_attr_list): Rename into prepend_attributes to allow
	cumulating attributes for different entities into a single list.
	(gnat_to_gnu_entity): Use prepend_attributes to build the list of
	attributes for the current entity and propagate first subtype
	attributes to other subtypes.
	<E_Procedure>: Attribute arguments are attr->args and not
	attr->arg any more.
	(build_attr_list): Ditto. Make attr->args a TREE_LIST when there is an
	argument provided, as this is what GCC expects. Use NULL_TREE instead
	of 0 for trees.

From-SVN: r90900