1 vs. 2 rounds of Cps simplification

[Stephen Weeks]

Here are the running times and code sizes comparing running the Cps
simplifier 1 or 2 rounds.  There was notable improvement in logic
(20%) and simple (33%).  I don't think this justifies running the
simplifier twice in general, but it's probably worth looking into
those cases that did speed up to understand why and maybe change the
phase ordering or add an extra pass.

		
		   time(s)        size(bytes)
		 1	 2	  1	  2
		----	----	------	------
barnes-hut	13.8	13.8	 40675	 39043
count-graphs	12.8	12.7	 40621	 40793
fft		39.6	35.1	 26393	 23541
knuth-bendix	26.8	26.2	 70334	 69878
lexgen		48.8	48.2	187519	184327
life		57.6	54.6	 37181	 36005
logic		52.8	42.1	363741	415021
mandelbrot	16.3	16.3	 12965	 12965
matrix-multiply	13.3	13.1	 13577	 13577
mlyacc		24.6	23.9	840215	817287
nucleic		24.3	29.9	 52807	 74567
ratio-regions	25.4	24.3	 40601	 40113
simple		21.0	14.9	337544	274452
tsp		30.6	30.7	 30591	 30495
vliw		21.5	20.6	927819	889351
zern		44.9	45.1	 21234	 20634