To support subclasses that may extend the falco rules format, add
additional error/warning/item types for an extension item.
When subclasses report errors and warnings, they can use these
codes/item types in context objects and still provide an exact
line/column context.
Also make some previously static functions in rules reader protected
methods so they can be used in sub-classes.
Signed-off-by: Mark Stemm <mark.stemm@gmail.com>
ce5a50cbb5