/*
 *  call-seq:
 *     dvector.each {|x| block }   ->   dvector
 *  
 *  Calls <i>block</i> once for each element in _dvector_, passing that
 *  element as a parameter.
 *     
 *     a = Dvector[ 1, 0, -1 ]
 *     a.each {|x| print x, " -- " }
 *     
 *  produces:
 *     
 *      1 -- 0 -- -1 --
 */ VALUE dvector_each(VALUE ary) {