* varpool.c (dump_varpool_node): Dump used_by_single_function.
	* tree-pass.h (make_pass_ipa_single_use): New pass.
	* cgraph.h (used_by_single_function): New flag.
	* lto-cgraph.c (lto_output_varpool_node, input_varpool_node): Stream
	it.
	* passes.def (pass_ipa_single_use): Scedule.
	* ipa.c (BOTTOM): New macro.
	(meet): New function
	(propagate_single_user): New function.
	(ipa_single_use): New function.
	(pass_data_ipa_single_use): New pass.
	(pass_ipa_single_use): New pass.
	(pass_ipa_single_use::gate): New gate.
	(make_pass_ipa_single_use): New function.

From-SVN: r211925