[Maxima] stacking two matrices

[Stavros Macrakis]

> Thanks, Robert!  I keep making the erroneous assumption that since
> Maxima is intrinsically Lispy; it should be extrinsically Lispy, too.

Maxima is implemented in Lisp, and much of the language semantics are
based directly on Lisp as of the late 1960's.  In Maclisp, nested
function definitions weren't local, either....

> One more thing, Robert: I take it that tail recursion is quite out.

Tail recursion is just fine, but it is not optimized: the stack grows
on every recursion.

              -s