Misra: Add tools and description to use cppcheck

Add a python script transforming the Zephyr coding guidelines into a cppcheck compatible list of misra rules description.

Add a README file describing how to generate the rules and run cppcheck.

Add a patch to add cppcheck support to Xen.

Update Zephyr Coding guidelines to the latest one from Master

Signed-off-by: Bertrand Marquis bertrand.marquis@arm.com