``desing/gb``

This is a procedure performs Gröbner basis computation using the
package selected by `desingcfg[gblib]`.

**Input:**-
**F**- a list of polynomials in the variables [op(B1),op(B2)],
**B1**- the first block of variables of the ordering
**B2**- the second block of variables of the ordering

At least one of the blocks must contain a variable and then the
defined ordering is the block degree-reverse-lexicographic one with
B1-variables being bigger than B2-ones.
**Output:**- A list of polynomials forming a Gröbner basis for the
input with respect to the given ordering.