pgsql: Add SQL type xid8 to expose FullTransactionId to users.

Add SQL type xid8 to expose FullTransactionId to users.

Similar to xid, but 64 bits wide.  This new type is suitable for use in
various system views and administration functions.

Reviewed-by: Fujii Masao <masao.fujii@oss.nttdata.com>
Reviewed-by: Takao Fujii <btfujiitkp@oss.nttdata.com>
Reviewed-by: Yoshikazu Imai <imai.yoshikazu@fujitsu.com>
Reviewed-by: Mark Dilger <mark.dilger@enterprisedb.com>
Discussion: https://postgr.es/m/20190725000636.666m5mad25wfbrri%40alap3.anarazel.de

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/aeec457de8a8820368e343e791accffe24dc7198

Modified Files
--------------
doc/src/sgml/datatype.sgml               |   7 ++
src/backend/access/hash/hashvalidate.c   |   3 +
src/backend/utils/adt/xid.c              | 116 ++++++++++++++++++++++++++
src/fe_utils/print.c                     |   1 +
src/include/access/transam.h             |  14 ++++
src/include/catalog/catversion.h         |   2 +-
src/include/catalog/pg_amop.dat          |  22 +++++
src/include/catalog/pg_amproc.dat        |   8 ++
src/include/catalog/pg_cast.dat          |   4 +
src/include/catalog/pg_opclass.dat       |   4 +
src/include/catalog/pg_operator.dat      |  25 ++++++
src/include/catalog/pg_opfamily.dat      |   4 +
src/include/catalog/pg_proc.dat          |  36 ++++++++
src/include/catalog/pg_type.dat          |   4 +
src/include/utils/xid8.h                 |  22 +++++
src/test/regress/expected/opr_sanity.out |   7 ++
src/test/regress/expected/xid.out        | 136 +++++++++++++++++++++++++++++++
src/test/regress/parallel_schedule       |   2 +-
src/test/regress/serial_schedule         |   1 +
src/test/regress/sql/xid.sql             |  48 +++++++++++
20 files changed, 464 insertions(+), 2 deletions(-)