bumped simplecpp to https://github.com/danmar/simplecpp/commit/9dc2c3df53ee0caf76906e596306f7ad70fc2a78 by firewave · Pull Request #4726 · cppcheck-opensource/cppcheck

The changed test result is expected since when I wrote the test I assumed that "system header may be relative to source file" is actually valid. Since this has been (correctly) removed from simplecpp the test failed.

That fix has been extracted from #4704 which will increase the test coverage of missing includes.