segfault in QuadMesh with Numeric

Starting from CVS mpl, I tested examples/

    > and found that it worked only with numarray; Numeric and
    > numpy refused to cast the Float64 X and Y arrays to Float32.
    > So I fixed that in CVS by using the astype method. Now the
    > demo works with numpy and numarray, but segfaults with
    > Numeric. I have not tried to track the problem down; it is
    > very low priority for me. Given the momentum towards numpy,
    > it might not be worth tracking down at all.

I'm a little hesitant to leave in a segfault because they can be
very difficult to track down. Perhaps Alex and/or Paul can address

If it proves too difficult, we should at least check for Numeric in
calls to quadmesh and generate a warning before the segfault occurs.