/*
 *  call-seq:
 *     dvector.delete_if {|x| block }  -> dvector
 *  
 *  Deletes every element of _dvector_ for which <i>block</i> evaluates
 *  to <code>true</code>.
 *     
 *     a = Dvector[ 1, 2, 3, 4 ]
 *     a.delete_if {|x| x.modulo(2) == 0 }   -> Dvector[1, 3]
 *     a                                     -> Dvector[ 1, 3 ]
 */ 
VALUE dvector_delete_if(VALUE ary) {