Snd 24.7:

s7: added complex-vectors. These are directly compatible with gsl_vector_complex.

  make-iterator's optional third argument can be #t which tells s7
  to choose the carrier based on the iterated sequence.

  s7_immutable has been deprecated, replaced by s7_set_immutable which
  has the necessary s7_scheme* argument.

  added s7_define_expansion.

checked: sbcl 2.4.8

Thanks!: Matthew
