CheckerGccPlugins: Updates
Add -config command-line switch to allow specifying more config files.
Add a configuration flag to enable warnings for calls to unchecked functions.
Don't do thread-safety checking in headers included via -isystem. Add some additional patterns of generated dictionaries for which we should not do thread-safety checking.
Add Converter::initialize and Converter::finalize as exceptions to virtual override checking.
Fix compilation against gcc 11.3.
Supercedes !963 (closed).