replaced uses of the 1//2 macro with the 1//2 variable.
replaced uses of the half macro with the variable 1//2.
removed the i//2 and min%i macros in opers.lisp, since they weren't used
x1 and y1 were not used in facrtimes, so declared them to be ignored.
chenged pflatten do use a do loop instead of go.
removed knownfactors. the function wasn't used anywhere.
changed dopgcdcofacts to return multiple values and replaced the use of
minor cosmetic changes.