matmin and matmax return a vector of length
nrow(cbind(...)). matsort returns a matrix of dimension
dim(cbind(...)) with in each row of cbind(...) sorted.
matsort(x) is a lot faster than, e.g., t(apply(x,1,sort)),
if x is tall (i.e., nrow(x)>>ncol(x) and
ncol(x)<30. If ncol(x)>30 then matsort simply calls
`t(apply(x,1,sort))'. matorder returns a permutation which
rearranges its first argument into ascending order, breaking ties by
further arguments.