pgsql: Add a way to get the current function's OID in pl/pgsql.

Add a way to get the current function's OID in pl/pgsql.

Invent "GET DIAGNOSTICS oid_variable = PG_ROUTINE_OID".
This is useful for avoiding the maintenance nuisances that come
with embedding a function's name in its body, as one might do
for logging purposes for example. Typically users would cast the
result to regproc or regprocedure to get something human-readable,
but we won't pre-judge whether that's appropriate.

Pavel Stehule, reviewed by Kirk Wolak and myself

Discussion: https://postgr.es/m/CAFj8pRA4zMd5pY-B89Gm64bDLRt-L+akOd34aD1j4PEstHHSVQ@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/d3d53f955cf6ad755ba3682577e0f6fa10106438

Modified Files
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doc/src/sgml/plpgsql.sgml | 5 +++++
src/pl/plpgsql/src/pl_exec.c | 6 ++++++
src/pl/plpgsql/src/pl_funcs.c | 2 ++
src/pl/plpgsql/src/pl_gram.y | 6 ++++++
src/pl/plpgsql/src/pl_unreserved_kwlist.h | 1 +
src/pl/plpgsql/src/plpgsql.h | 1 +
src/test/regress/expected/plpgsql.out | 31 +++++++++++++++++++++++++++++--
src/test/regress/sql/plpgsql.sql | 29 +++++++++++++++++++++++++++--
8 files changed, 77 insertions(+), 4 deletions(-)