Peano: move division and minmax into separate modules

examples/avl/avl/why3session.xml

examples/avl/avl/why3shapes.gz

examples/avl/monoid/why3session.xml

examples/avl/monoid/why3shapes.gz

examples/avl/preorder/why3session.xml

examples/avl/priority_queue/why3session.xml

examples/avl/priority_queue/why3shapes.gz

examples/avl/ral/why3session.xml

examples/avl/ral/why3shapes.gz

examples/avl/tables/why3session.xml

examples/avl/tables/why3shapes.gz

examples/mccarthy.mlw

examples/mccarthy/why3session.xml

examples/mccarthy/why3shapes.gz

examples/mccarthy_vc_sp/why3shapes.gz

examples/vstte10_queens/why3session.xml

examples/vstte10_queens/why3shapes.gz

stdlib/mach/peano.mlw