Computation of the list of monomials up to a given degree in a
The procedure uses the global variable, desingmonseq, which
has to be set to the empty list before calling the the procedure. The
resulting monomial sequence is obtained in the desingmonseq
- the list of variables to build monomials
- the monomial which is computed in the previous recursive
call (it should be set to 1 at the initial call),
- the degree up to which generate monomials.