Add recomputation to outgoing_edge_range.

Add recomputation to outgoing_edge_range.

The gori engine can calculate outgoing ranges for exported values.  This
change allows 1st degree recomputation.  If a name is not exported from a
block, but one of the ssa_names used directly in computing it is, then
we can recompute the ssa_name on the edge using the edge values for its
operands.

	* gimple-range-gori.cc (gori_compute::has_edge_range_p): Check with
	may_recompute_p.
	(gori_compute::may_recompute_p): New.
	(gori_compute::outgoing_edge_range_p): Perform recomputations.
	* gimple-range-gori.h (class gori_compute): Add prototype.