Function: listsort
Section: programming/specific
C-Name: listsort
Prototype: vWD0,L,
Help: listsort(L,{flag=0}): sort the list L in place. If flag is non-zero,
 suppress all but one occurence of each element in list.
Doc: sorts the \typ{LIST} \var{list} in place, with respect to the (somewhat
 arbitrary) universal comparison function \tet{cmp}. In particular, the
 ordering is the same as for sets and \tet{setsearch} can be used on a sorted
 list.
 \bprog
 ? L = List([1,2,4,1,3,-1]); listsort(L); L
 %1 = List([-1, 1, 1, 2, 3, 4])
 ? setsearch(L, 4)
 %2 = 6
 ? setsearch(L, -2)
 %3 = 0
 @eprog\noindent This is faster than the \kbd{vecsort} command since the list
 is sorted in place: no copy is made. No value returned.

 If $\fl$ is non-zero, suppresses all repeated coefficients.
