The new method uses a table and the taylor series for atan to compute
atan for real args.

qd-const.lisp:
o Add the two tables used for the atan computation.
o Include clisp code that generates the tables.

qd-fun.lisp:
o Implement atan using a set of tables and a Taylor series.

timing.lisp:
o Add a simple timing program to evaluate how fast each atan method
  is.

oct.asd:
o qd-const2 depends on qd-const.

qd-const.lisp:
o Add qd value for Euler's constant

qd-const2.lisp:
o Add qd-real value for Euler's constant.

can't multiple-value-call it.  Rearrange code accordingly.

qd-fun.lisp:
o Comment out the old sin/cos routines
o Fix a few mistakes in accurate-sincos-qd
o Rename accurate-sincos-qd to sincos-qd.

o Add code for clisp to create the constants we need.  (Clisp has
  arbitrary length long-float numbers.)
o Update the constants accordingly.
o Move the atan table stuff for CORDIC to qd-extra.lisp, since we
  don't need them in oct itself.

qd-extra.lisp:
o atan table stuff for CORDIC moved here.

o Get rid of the #q reader that returns an internal %qd-real.

qd-methods.lisp:
o QPHASE was returning the wrong kind of object for positive values.
o Replace use of #q0 with the construction of a qd-real 0.

qd-const.lisp:
o Replace all uses of #q with #.(qd-from-string ...).

  to get around issues with bad floating-point readers in some lisps.
o Add DUMP-QD to create the appropriate %make-qd-d form for a
  double-float to help with the above conversion.

  qd.lisp and friends
o create QUAD-DOUBLE package for the quad-double class.
o Update in-package forms appropriately.
o Export the necessary QUAD-DOUBLE-INTERNAL symbols so QUAD-DOUBLE can
  use them.

o Add +QD-ZERO+ and +QD-ONE+

qd-fun.lisp:
o Use the new constants as needed
o Use PLUSP-QD instead of QD->.
o Update timing info with PPC results.

+qd-log2+ so that the sum of the two is log(2) to twice the precision
of quad-double.

o Fix up extra paren
o Add +CORDIC-SCALE+

  truncating.
o Make the atan table and power table start with atan(4) and 4.  This
  allows the cordic routine to handle all angles.  (I think).

o The atan-power-table can be represented exactly using double-floats,
  instead of quad-doubles.

functions.