pgsql: pg_buffercache: Change page_num type to bigint

pg_buffercache: Change page_num type to bigint

The page_num was defined as integer, which should be sufficient for the
near future (with 4K pages it's 8TB). But it's virtually free to return
bigint, and get a wider range. This was agreed on the thread, but I
forgot to tweak this in ba2a3c2302f1.

While at it, make the data types in CREATE VIEW a bit more consistent.

Discussion: https://postgr.es/m/CAKZiRmxh6KWo0aqRqvmcoaX2jUxZYb4kGp3N%3Dq1w%2BDiH-696Xw%40mail.gmail.co

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/91f1fe90c7d42641201bd2c474bd86d703b5e830

Modified Files
--------------
contrib/pg_buffercache/pg_buffercache--1.5--1.6.sql | 2 +-
contrib/pg_buffercache/pg_buffercache_pages.c | 6 +++---
doc/src/sgml/pgbuffercache.sgml | 2 +-
3 files changed, 5 insertions(+), 5 deletions(-)