qd-io.lisp:

o Add RATIONAL-TO-QD, a simple, fast and accurate method to convert
  rationals to quad-doubles.  (From Richard Fateman.)
o Use RATIONAL-TO-QD to create a quad-float

qd-methods.lisp:
o Use RATIONAL-TO-QD to create a quad-float from a bignum and ratio.

qd-package.lisp:
o Export RATIONAL-TO-QD