Add naive and horribly performing port of Haskell's fasta benchmark implementation

This benchmark is part of the 'computer benchmarks game'
(http://benchmarksgame.alioth.debian.org/).
Replace Nat's with Int's

The performance of Nat's is prohibitive
Replace awful scanl version with a saner one
Fix bugs in fasta implementation
Add fasta benchmark to benchmarks/ALL
Merge pull request #1084 from paulkoerbitz/add-fasta-benchmark

Add fasta benchmark