Syntax: SORT { vector_list }
or      SORT < vector_list >
or      SET vec = SORT ( expr )

   Sort the first vector in the list into increasing numerical order,
and rearrange the others in the same way. The maximum number of
vectors that can be sorted is 10.

Any mixture of string- integral- and arithmetic-valued vectors is allowed.

   You can also use SORT as a function in an expression.
