/*
 *  call-seq:
 *     dvector.acosh!   ->  dvector
 *  
 *  Replace each entry x of _dvector_ with acosh(x).
 *     
 *     a = Dvector[ 1.1, 2.2, 5.3 ]
 *     a.acosh!   -> Dvector[ acosh(1.1), acosh(2.2), acosh(5.3) ]
 *     a          -> Dvector[ acosh(1.1), acosh(2.2), acosh(5.3) ]
 */ 
VALUE dvector_acosh_bang(VALUE ary) {