Remove all "INTERFACE ROUTINES" style comments

Hi,

A number of postgres files have sections like heapam's

 * INTERFACE ROUTINES
 *      relation_open   - open any relation by relation OID
 *      relation_openrv - open any relation specified by a RangeVar
 *      relation_close  - close any relation
 *      heap_open       - open a heap relation by relation OID
 *      heap_openrv     - open a heap relation specified by a RangeVar
 *      heap_close      - (now just a macro for relation_close)
 *      heap_beginscan  - begin relation scan
 *      heap_rescan     - restart a relation scan
 *      heap_endscan    - end relation scan
 *      heap_getnext    - retrieve next tuple in scan
 *      heap_fetch      - retrieve tuple with given tid
 *      heap_insert     - insert tuple into a relation
 *      heap_multi_insert - insert multiple tuples into a relation
 *      heap_delete     - delete a tuple from a relation
 *      heap_update     - replace a tuple in a relation with another tuple
 *      heap_sync       - sync heap, for when no WAL has been written

They're often out-of-date, and I personally never found them to be
useful. A few people, including yours truly, have been removing a few
here and there when overhauling a subsystem to avoid having to update
and then adjust them.

I think it might be a good idea to just do that for all at once. Having
to consider separately committing a removal, updating them without
fixing preexisting issues, or just leaving them outdated on a regular
basis imo is a usless distraction.

Comments?

Greetings,

Andres Freund