Add port of Levent's s-expression printer
Add port of Levent's s-expression printer

This allows for more efficient pretty-printing of SAWCore terms, with a depth
limit. It's not very pretty yet, and probably doesn't handle all alternatives
in the best way, but it's already useful for understanding large terms.
GaloisInc/saw-script,GaloisInc/saw-script,GaloisInc/saw-script,GaloisInc/saw-script,GaloisInc/saw-script