pcr: Add aflplusplus
    
    The AFL website[1] states the following:
        Note: AFL hasn't been updated for a couple of years; while it
        should still work fine, a more complex fork with a variety of
        improvements and additional features, known as AFL++, is available
        from other members of the community and might be worth checking
        out.
    [1]https://lcamtuf.coredump.cx/afl/
    
    Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>