Export global ranges during the VRP block walk.

Export global ranges during the VRP block walk.

VRP currently searches the ssa_name list for globals to exported after it
finishes running.  Recent changes have VRP calling a side-effect routine for
each stmt during the walk.  This change simply exports globals as they are
calculated the final time during the walk.

	* gimple-range.cc (gimple_ranger::register_side_effects): First check
	if the DEF should be exported as a global.
	* tree-vrp.cc (rvrp_folder::pre_fold_bb): Process PHI side effects,
	which will export globals.
	(execute_ranger_vrp): Remove call to export_global_ranges.