/*
 *  call-seq:
 *  dvector.include?(number)   -> true or false
 *  
 *  Returns <code>true</code> if _number_ is present in
 *  _dvector_, <code>false</code> otherwise.
 *     
 *     a = Dvector[ 1, 2, 3 ]
 *     a.include?(2)   -> true
 *     a.include?(0)   -> false
 */ 
VALUE dvector_includes(VALUE ary, VALUE item) {