/*
 *  call-seq:
 *     dvector.insert(int, number...)  -> dvector
 *  
 *  If the index is not negative, insert the given values before
 *     the element with the index _int_.  If the index is -1, appends the
 *     values to _dvector_.  Otherwise inserts the values after the element
 *    with the given index.
 *
 *     a = Dvector[ 1, 2, 3 ]
 *     a.insert(2, 99)         -> Dvector[ 1, 2, 99, 3 ]
 *     a.insert(-2, 1, 2, 3)   -> Dvector[ 1, 2, 99, 1, 2, 3, 3 ]
 *     a.insert(-1, 0)         -> Dvector[ 1, 2, 99, 1, 2, 3, 3, 0 ]
 */ VALUE dvector_insert(int argc, VALUE *argv, VALUE ary) {