pgsql: Rename bytea_agg to string_agg and add delimiter argument

Rename bytea_agg to string_agg and add delimiter argument

Per mailing list discussion, we would like to keep the bytea functions
parallel to the text functions, so rename bytea_agg to string_agg,
which already exists for text.

Also, to satisfy the rule that we don't want aggregate functions of
the same name with a different number of arguments, add a delimiter
argument, just like string_agg for text already has.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/c0cc526e8b1e821dfced692a68e4c8978c2bdbc1

Modified Files
--------------
doc/src/sgml/func.sgml | 27 ++++++------------------
src/backend/utils/adt/varlena.c | 13 +++++++++--
src/include/catalog/catversion.h | 2 +-
src/include/catalog/pg_aggregate.h | 2 +-
src/include/catalog/pg_proc.h | 6 ++--
src/include/utils/builtins.h | 4 +-
src/test/regress/expected/aggregates.out | 32 ++++++++++++++++++++---------
src/test/regress/sql/aggregates.sql | 10 +++++---
8 files changed, 52 insertions(+), 44 deletions(-)