Fix new warnings
Following update of command line tools and PETSc library, I get spurious warnings that needs to be deactivated:
- Wformat-nonliteral
- Wformat-security
So these warnings have been added in the list of those that could be ignore.
Currently it is:
- Activated only for clang
- Using the facility I discovered recently to properly deal with version support or not:
__has_warning