LP#1997485: Include authority headings in symspell dict

LP#1997485: Include authority headings in symspell dict

This patch adjusts the generation of search suggestions
based on authority headings by:

* Including all indexed authority headings (1XX, 4XX, and 5XX) from
  authority records for author, title, and subject headings in the
  search suggestion dictionary.
* As a consequence, suggestions can be based entirely on headings
  found in authority 4XX and 5XX fields without those headings
  also needing to be directly in at least one bibliographic record.

Signed-off-by: Mike Rylander <mrylander@gmail.com>
Signed-off-by: Galen Charlton <gmc@equinoxOLI.org>