Problem with free summands (related to #363)

[barakat@…]

Singular seems to handle free summands incorrectly, this is related to the trac ticket

www.singular.uni-kl.de:8002/trac/ticket/363

This could be a source of many bugs. Here is one more:

                     SINGULAR                                 /  Development
 A Computer Algebra System for Polynomial Computations       /   version 3-1-3
                                                           0<
 by: W. Decker, G.-M. Greuel, G. Pfister, H. Schoenemann     \   March 2011
FB Mathematik der Universitaet, D-67653 Kaiserslautern        \
// ** executing /Users/mo/software/singular/Singular/LIB/.singularrc
) ring r=0,(x,y),dp;
) matrix m0[1][2]=x,y;
) dim(m0);
// ** _ is no standard basis
0
) matrix m1[2][3]=x,y,0, 0,0,x;
) dim(m1);
// ** _ is no standard basis
1
) matrix m2[3][3]=x,y,0, 0,0,x, 0,0,0;
 dim(m2);
// ** _ is no standard basis
1

expected 2