Consistently use named parameters in regex code.

Consistently use named parameters in regex code.

Make regex code consistently use named parameters in function
declarations.  Also make sure that parameter names from each function's
declaration match corresponding definition parameter names.

This makes Henry Spencer's regex code follow Postgres coding standards.

Author: Peter Geoghegan <pg@bowt.ie>
Reviewed-By: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/CAH2-WznJt9CMM9KJTMjJh_zbL5hD9oX44qdJ4aqZtjFi-zA3Tg@mail.gmail.com