problem with genmarshal rules in libbonobo

[Darin Adler <darin bentspoon com>]

I noticed that the genmarshal rules in libbonobo use a cmp command to 
check if gnome-canvas-marshal.h is the same as last time, and leave it 
untouched if so.

The problem with this is that if bonobo-marshal.list is newer than 
bonobo-marshal, this means that genmarshal will be run every single time, 
since bonobo-marshal.h will never get touched. So I think the "don't 
overwrite if identical" optimization doesn't really make things better. I'
m not sure how to get this right. It may be impossible, given how make 
works, or some trick with a timestamp file might work (unlikely, since the 
dependency on bonobo-marshal.h is part of the automatic header depedencies)
.

    -- Darin