/*
 *  call-seq:
 *     dvector.round!   ->  dvector
 *  
 *  Replace each entry x of _dvector_ with the integer closest to x.
 *  (Numbers midway between integers round away from zero.)
 *     
 *     a = Dvector[ 1.1, -2.2, 5.3 ]
 *     a.round!   -> Dvector[ 1, -2, 5 ]
 *     a          -> Dvector[ 1, -2, 5 ]
 */ 
VALUE dvector_round_bang(VALUE ary) {