In cparser/SimplExpr.ml:

- wrong simplification of && and || in the Set case
- generated nicer code for && and || in the Eval case


git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@1308 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e