4.20 smatrix

An experimental type:
Objects of type smatrix are (sparse) matrices with polynomial entries. Like polynomials they can only be defined or accessed with respect to a basering.

Objects of type smatrix can be converted to and from matrix and module.
Operations are +, -, *, ==, <>.
Functions are chinrem, farey, ncols, nrows, std, transpose, tensor. Additional flatten(m) and system("unflatten",m,col).
Resizing can be done via smatrix(m,r,c) where m is of type module or smatrix.
Access to single entries: m[i,j]

See chinrem; farey; flatten; matrix; module; ncols; nrows; ring; std; tensor; transpose.