Trac 15815: fix rational_preimages for projective morphism
trac 15815: fixed doc test
Trac 13048: fixed division without remainder for polynomials over QQbar
Trac #13048: __floordiv__ does not work when dividing polynomials over QQbar by a constant

There is a problem with {{{//}}} division for polynomials over QQbar:

{{{
sage: R.<x> = QQbar[]
sage: x//1
AttributeError: 'Polynomial_generic_dense_field' object has no attribute
'_new_c'
sage: x/1
x
}}}

URL: http://trac.sagemath.org/13048
Reported by: saraedum
Ticket author(s): Julian Rueth
Reviewer(s): Douglas McNeil, Marc Mezzarobba
Trac #15815: rational preimages for projective morphisms returns incorrect points

The function rational_preimages for projective morphism polynomials,
returns points that are not
pre-images of the input points. The issue is that the solutions found
may only be solutions to
some of the equations in the ideal.

I will add a check to insure only correct points are returned.

URL: http://trac.sagemath.org/15815
Reported by: bhutz
Ticket author(s): Ben Hutz
Reviewer(s): Joao Alberto de Faria