/*
 *  call-seq:
 *     dvector << number  -> dvector
 *  
 *  Append---Pushes the given number on to the end of this vector. This
 *  expression returns the vector itself, so several appends
 *  may be chained together.
 *
 *     Dvector[ 1, 2 ] << -3.3 << 1e3    ->  Dvector[ 1, 2, 3.3, 1000.0 ]
 *
 */ VALUE dvector_push(VALUE ary, VALUE item) {