Mmin(), Mmax()

Mmin() and Mmax() calculate the min and max of matrices. They also return the index of values: 
   if marg = ALL      return 3x1   [ maxr, maxc, max element ]
   if marg = ROWS     return 3xc   Tran([ maxr, col=1..c, max element ])
   if marg = COLUMNS  return rx3   [ row=1..r, maxc, max element]
where maxr is the index of the row max, maxc is the index of the column max, and max element is the maximum. Mmin() functions similarly, but returns mininums and their indices.