* Historically, n-fixnum-tag-bits has been equal to word-shift and has
been (1- n-lowtag-bits). This led to implementors using constants and
calculations which happened to be right by coincidence rather than by
* Fix all places not part of the support for a particular backend to
use the defined-correct constants and calculations for the operations
* Thanks to Paul Khuong for helping with the finding and fixing of
many of these coincidences.