vecsort() shortdocs

[I vaguely remember reporting this already a few years ago.]

On 2.15.5, pressing F1 on vecsort() says:

  vecsort(x,{cmpf},{flag=0}): sorts the vector of vectors (or matrix)
  x in ascending order

 — but vecsort() operates happily on vectors of numbers as well.

Hope this helps,
Ilya