pgsql: Add FOREACH IN ARRAY looping to plpgsql.

Add FOREACH IN ARRAY looping to plpgsql.

(I'm not entirely sure that we've finished bikeshedding the syntax details,
but the functionality seems OK.)

Pavel Stehule, reviewed by Stephen Frost and Tom Lane

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/6e02755b22ea62775c906d29b87b55b38ab70bd2

Modified Files
--------------
doc/src/sgml/plpgsql.sgml             |  106 +++++++++++++++--
src/backend/utils/adt/arrayfuncs.c    |  206 +++++++++++++++++++++++++++++++++
src/include/utils/array.h             |    7 +
src/pl/plpgsql/src/gram.y             |   63 ++++++++++-
src/pl/plpgsql/src/pl_exec.c          |  185 +++++++++++++++++++++++++++++
src/pl/plpgsql/src/pl_funcs.c         |   23 ++++
src/pl/plpgsql/src/pl_scanner.c       |    3 +
src/pl/plpgsql/src/plpgsql.h          |   13 ++
src/test/regress/expected/plpgsql.out |  194 +++++++++++++++++++++++++++++++
src/test/regress/sql/plpgsql.sql      |  114 ++++++++++++++++++
10 files changed, 899 insertions(+), 15 deletions(-)