Data flow: Prune parameter-self flow in stage 1

[hvitved]

Example tuple counts (~10 % reduction in stage 1):

Before

#	n	stage	nodes	fields	conscand	states	tuples	calledges	tfnodes	tftuples
1	10	1 Fwd	3,530,293	37,778	-1	1	5,111,856	-1	-1	-1
2	15	1 Rev	2,195,396	29,094	-1	1	3,366,038	2,078,437	-1	-1
3	20	2 Fwd	668,068	5,322	6,521	1	1,291,454	516,310	0	0
4	25	2 Rev	351,997	3,170	3,673	1	526,910	125,603	0	0
5	30	3 Fwd	19,865	75	89	1	27,492	6,212	1,108	2,127

After

#	n	stage	nodes	fields	conscand	states	tuples	calledges	tfnodes	tftuples
1	10	1 Fwd	3,460,957	37,591	-1	1	4,764,986	-1	-1	-1
2	15	1 Rev	2,135,520	28,847	-1	1	2,992,383	2,042,022	-1	-1
3	20	2 Fwd	654,633	5,189	6,316	1	1,274,172	509,370	0	0
4	25	2 Rev	349,487	3,144	3,641	1	522,787	124,824	0	0
5	30	3 Fwd	19,803	74	88	1	27,397	6,194	1,103	2,122