Function: listsort
Section: linear_algebra
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. If $\fl$ is non-zero,
 suppresses all repeated coefficients. This is faster than the \kbd{vecsort}
 command since no copy has to be made. No value returned.
