PR#6042: optimize integer division and modulus when divisor is constant.
So far, implemented only for amd64.


git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@14254 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
Follow-up to commit r14254: update destroyed_at_oper and max_register_pressure
for immediate Idiv and Imod.


git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@14255 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02