[Maxima] possible bug with integration of unit_step

[Robert Dodier]

Barton,

I'm guessing something got broken recently (around Dec 6).
I have builds dated Dec 5 w/ cvs Maxima + GCL and SBCL,
and those do not show the bug. But builds dated Dec 7 w/
CMUCL and Clisp, and Dec 12 w/ ECL, do show it.
I 'm pretty sure 5.17.1 (branched Dec 1) does not.

HTH

Robert