#11: extend flonum->string to support optional precision arg to support SRFI-48; improve flonum printing accordingly
#10: bug: (floor-quotient 1 -1) actual: -2 expected: -1
#9: immediate-hash should hash flonums even if they are boxed
#8: string-append and vector-append with 1 arg must copy the arg
#7: stop advertising built-in support for SRFI-48, allowing full external implementation
#6: expt should fall back to flonums on fixnum range overflow