* Bug 16197 fixed: decomplexify result of extraction when applicable

* Bug 16197 fixed: decomplexify result of extraction when applicable

https://bugzilla.scilab.org/show_bug.cgi?id=16197

If after extraction imaginary parts of result are all zero then result
is decomplexified. The patch does not interfer with other features like

--> x=complex(zeros(3,1)) // no extraction here
 x  =

   0.
   0.
   0.

--> isreal(x)
 ans  =

  F

but it allows the intuive behaviors below:

--> p=poly([1 1 1 1],"x","coeff"); r=roots(p)
 r  =

   1.i
  -1.i
  -1.

--> isreal(r(3))
 ans  =

  T

Change-Id: Ieed42028fbe36540a549f6f3d3dd7325c370a210