Remove rows or columns of a matrix : delrows delcols

### 2.42.15 Remove rows or columns of a matrix : `delrows delcols`

`delrows` (resp `delcols`) removes one or several rows (resp columns) of a matrix.
`delrows` (resp `delcols`) takes 2 arguments : a matrix A, and an interval n1..n2.
`delrows` (resp `delcols`) returns the matrix where the rows (resp columns) of index from n1 to n2 of A are removed.
Input :

`delrows([[1,2,3],[4,5,6],[7,8,9]],1..1)`

Output :

`[[1,2,3],[7,8,9]]`

Input :

`delrows([[1,2,3],[4,5,6],[7,8,9]],0..1)`

Output :

`[[7,8,9]]`

Input :

`delcols([[1,2,3],[4,5,6],[7,8,9]],1..1)`

Output :

`[[1,3],[4,6],[7,9]]`

Input :

`delcols([[1,2,3],[4,5,6],[7,8,9]],0..1)`

Output :

`[[3],[6],[9]]`