re PR c/28744 (externally_visible attribute not effective with prior declaration...

re PR c/28744 (externally_visible attribute not effective with prior declaration of symbol.)

	PR c/28744
	* cgraph.h (struct cgraph_node): Remove externally_visible
	bitfield.
	* cgraphunit.c (process_function_and_variable_attributes): Set
	local.externally_visible rather than externally_visible.

	PR c/28744
	* c-common.c (handle_externally_visible_attribute): First look
	at TREE_CODE and only if it is function or var decl, check for
	non-public objects.  Don't warn for DECL_EXTERNAL.
	* cgraphunit.c (process_function_and_variable_attributes): Warn
	if externally_visible attribute is used on non-public object.

	* gcc.dg/attr-externally-visible-1.c: New test.
	* gcc.dg/attr-externally-visible-2.c: New test.
	* g++.dg/parse/attr-externally-visible-1.C: New test.
	* g++.dg/parse/attr-externally-visible-2.C: New test.

From-SVN: r116222