pgsql: In plpgsql, allow %TYPE and %ROWTYPE to be followed by array dec

In plpgsql, allow %TYPE and %ROWTYPE to be followed by array decoration.

This provides the useful ability to declare a variable that is an array
of the type of some other variable or some table column.

Quan Zongliang, Pavel Stehule

Discussion: https://postgr.es/m/ec4523e1-9e7e-f3ef-f9ce-bafd680ad6f6@yeah.net

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/5e8674dc83926f52516f847f1a77e8d38e94e143

Modified Files
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doc/src/sgml/plpgsql.sgml                     | 29 ++++++++-
src/pl/plpgsql/src/expected/plpgsql_array.out | 79 ++++++++++++++++++++++++
src/pl/plpgsql/src/pl_comp.c                  | 27 +++++++++
src/pl/plpgsql/src/pl_gram.y                  | 86 ++++++++++++++++++---------
src/pl/plpgsql/src/plpgsql.h                  |  1 +
src/pl/plpgsql/src/sql/plpgsql_array.sql      | 71 ++++++++++++++++++++++
6 files changed, 261 insertions(+), 32 deletions(-)