Catch Additional Interp Headers

These account for two problematic situations in the interpretations:

1. We see "Appendices G and H" as well as a header for "Appendix G" and "Appendix H". This turns the former into XXXX-G:H-Interp.
2. When within an appendix' interpretation, headers sometimes indicate a paragraph without the appendix letter (e.g. `(b)(5) Some such`). This keeps the previously processed label around to provide context for these issues.