pgsql: Advance transaction timestamp for intra-procedure transactions.

Advance transaction timestamp for intra-procedure transactions.

Per discussion, this behavior seems less astonishing than not doing so.

Peter Eisentraut and Tom Lane

Discussion: https://postgr.es/m/20180920234040.GC29981@momjian.us

Branch
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REL_11_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/1145c26b749a73419d32e4c997237e84fbbffa04

Modified Files
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src/backend/access/transam/xact.c                  | 22 +++++++++------
src/backend/executor/spi.c                         | 13 +++++++++
src/include/executor/spi.h                         |  1 +
.../plpgsql/src/expected/plpgsql_transaction.out   | 30 ++++++++++++++++++++
src/pl/plpgsql/src/sql/plpgsql_transaction.sql     | 33 ++++++++++++++++++++++
5 files changed, 91 insertions(+), 8 deletions(-)