Lists, rationals, polynomials and intervals - Implementation (more functions)

Renames basic operations on lists.

Provides type rat : rational numbers and operations involving them.

Provides type rat_poly : polynomials in one variable and whose coefficients are rational numbers, and operations involving them.

Provides type rat_inter : singletons and non-empty open intervals whose bounds are rationals, and operations involving them.

Provides usual operations involving polynomials in one variable and whose coefficients are rational.

Provides operations involving the real roots of polynomials in one variable and whose coefficients are rational.

Provides some rat_poly values (polynomials in one variable and whose coefficients are rational numbers).