Instead of immediately constructing the string we need to emit into the
.BKI file, preserve the items we extracted from the header file in a hash.
This eases using the info for other purposes.

John Naylor (with cosmetic adjustments by me)

Discussion: https://postgr.es/m/37D774E4-FE1F-437E-B3D2-593F314B7505@postgrespro.ru