Sparse matrix problem

[michael . goffioul]

I notice that:
 
sparse(1+i) ./ sparse(0)  =>  NaN + NaNi
(instead of infinity).
 
This leads to several failures in the test regression suites. I tried on
2.1.73 under cygwin, with the same result. I also noticed the "FIXME"
in the sparse operators definitions, I guess it's related...
 
Michael.