/*
 *  call-seq:
 *     dvector.prune!(lst)  -> dvector
 *  
 *  Modifies the dvector by removing the entries given by the indexes in _lst_.
 *     
 *     a = Dvector.new(5) {|i| i*3 }    -> [0, 3, 6, 9, 12]
 *     a.prune!([0, 2])                 -> [3, 9, 12]
 *     a                                -> [3, 9, 12]
 */ 
VALUE dvector_prune_bang(VALUE ary, VALUE lst) {