pgsql: Include RelFileLocator fields individually in BufferTag.

Include RelFileLocator fields individually in BufferTag.

This is preparatory work for a project to increase the number of bits
in a RelFileNumber from 32 to 56.

Along the way, introduce static inline accessor functions for a couple
of BufferTag fields.

Dilip Kumar, reviewed by me. The overall patch series has also had
review at various times from Andres Freund, Ashutosh Sharma, Hannu
Krosing, Vignesh C, Álvaro Herrera, and Tom Lane.

Discussion: http://postgr.es/m/CAFiTN-trubju5YbWAq-BSpZ90-Z6xCVBQE8BVqXqANOZAF1Znw@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/82ac34db2036ec5b3cb32c9180f40549aa790dc2

Modified Files
--------------
contrib/pg_buffercache/pg_buffercache_pages.c | 8 +-
contrib/pg_prewarm/autoprewarm.c | 10 ++-
src/backend/storage/buffer/bufmgr.c | 115 +++++++++++++++-----------
src/backend/storage/buffer/localbuf.c | 21 +++--
src/include/storage/buf_internals.h | 64 ++++++++++++--
5 files changed, 145 insertions(+), 73 deletions(-)