PR#5707: in AMD64 port, exchange the roles of r10-r11 and r12-r13,
      so that r10 and r11 are no longer used for parameter passing,
      and can therefore be destroyed by the dynamic loader without harm.
    (Cherry-picked from version/4.00, commit 12907).
    
    
    git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@12908 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02