Choice exact-complexes

This choice is tested for by running

(number? (string->number "1+i"))

and

(exact? 1+1i)

in each Scheme.

• MIT Scheme, Scheme 48, RScheme, MzScheme and Gambit produce #t and #t
• Bigloo and Chicken produce #f and an error
• Guile, Gauche and Scm produce #t and #f