prtDataGenXor  Generates XOR example data
 
    DATASET = prtDataGenXor returns a prtDataSetClass with randomly
    generated data according to the following distribution.
 
        H0: N([-1 -1],eye(2))
        H1: N([2 2],[1 .5; .5 1])
 
    % Example
  
    ds = prtDataGenXor;
    plot(ds)