libgfs2: Move struct printing functions out of libgfs2
    
    Now that libgfs2 itself doesn't use these functions, they can be moved
    into the two utils that use them. This does duplicate the code but that
    means the utils are free to change the way that they're printed to suit
    their interfaces. We're still using the "print_it" extern that libgfs2.h
    requires but that can be removed next.
    
    Signed-off-by: Andrew Price <anprice@redhat.com>