/*
 *  call-seq:
 *     dvector.sqrt   ->  a_dvector
 *  
 *  Returns of copy of _dvector_ with each entry x replaced by sqrt(x).
 *     
 *     a = Dvector[ 1.1, 2.2, 5.3 ]
 *     a.sqrt   -> Dvector[ sqrt(1.1), sqrt(2.2), sqrt(5.3) ]
 */ 
VALUE dvector_sqrt(VALUE ary) {