pgsql: Rename a function to avoid naming conflict in parallel regressio

Rename a function to avoid naming conflict in parallel regression tests.

Commit 31a891857a128828d47d93c63e041f3b69cbab70 added some tests in
plpgsql.sql that used a function rather unthinkingly named "foo()".
However, rangefuncs.sql has some much older tests that create a function
of that name, and since these test scripts run in parallel, there is a
chance of failures if the timing is just right. Use another name to
avoid that. Per buildfarm (failure seen today on "hamerkop", but
probably it's happened before and not been noticed).

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/0cd787802f84583c4086b1af0a74015f230dfb70

Modified Files
--------------
src/test/regress/expected/plpgsql.out | 72 ++++++++++++++++-----------------
src/test/regress/sql/plpgsql.sql | 56 ++++++++++++-------------
2 files changed, 64 insertions(+), 64 deletions(-)