OLD fasta -n 25000000
	gcc -O2 fasta.c	7.59u 0.06s 7.74r
	gc fasta	9.54u 0.15s 9.84r
	gc_B fasta	9.48u 0.10s 9.62r

NEW fasta -n 25000000
	gcc -O2 fasta.c	2.59u 0.02s 2.66r
	gc fasta	3.00u 0.03s 3.09r
	gc_B fasta	2.72u 0.03s 2.81r

R=r
CC=golang-dev
https://golang.org/cl/1054041