[CM] CMN - straight flag problem in sbcl?

[andersvi at extern.uio.no]

>>>>> "B" == Bill Schottstaedt <bil at ccrma.Stanford.EDU> writes:

    B> Thanks very much for the bug report and bugfix!  I'll merge
    B> those changes into my versions later today.

It seems that sbcl's loop actually follows the specs (possibly for
optimization reasons?), requiring a positive value for the 'by
loop-keyword, necessitating choice of syntax dependent on direction of
stepping.

Cant remember what gcl complained about, but now that the 'do-version
of the code in #'draw-flags function does exactly the same as the
'loop-version there shouldnt be a need to dispatch on implementations
anymore.