The values are very unlikely to be EQL when redefining so just use
defparameter.  This is for picky compilers that don't like redefining
constants with values that aren't EQL.

  OCTI instead of QDI.
o Rename OCT package to NET.COMMON-LISP.OCT, with a nickname of OCT
o Remove nickname of QD.  (Conflicts with other packages dealing with
  quad-doubles.)
o Update all uses of QDI: to OCTI:

qd-fun.lisp:
o Add REM-PI/2 to do a simpler computation if the arg is small
  enough.  Otherwise, use the accurate but expensive rem operation.
o Renamed ACCURATE-SIN-QD to SIN-QD, etc.
o Update SIN-QD etc to use REM-PI/2.