pgsql: Clean up compiler warnings from unused variables with asserts di

Clean up compiler warnings from unused variables with asserts disabled

For those variables only used when asserts are enabled, use a new
macro PG_USED_FOR_ASSERTS_ONLY, which expands to
__attribute__((unused)) when asserts are not enabled.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/0e85abd658738db9ea183c133c89c3c94ee37dae

Modified Files
--------------
src/backend/access/hash/hashovfl.c       |    2 +-
src/backend/executor/execCurrent.c       |    2 +-
src/backend/executor/nodeMaterial.c      |    2 +-
src/backend/executor/nodeSetOp.c         |    2 +-
src/backend/executor/nodeWorktablescan.c |    4 +---
src/backend/libpq/be-fsstubs.c           |    2 +-
src/backend/libpq/pqcomm.c               |    2 +-
src/backend/optimizer/path/costsize.c    |    2 +-
src/backend/parser/analyze.c             |    2 +-
src/backend/storage/file/fd.c            |    2 +-
src/backend/storage/lmgr/predicate.c     |    6 +++---
src/backend/storage/lmgr/proc.c          |    2 +-
src/backend/utils/adt/selfuncs.c         |    4 ++--
src/bin/psql/psqlscan.l                  |    2 +-
src/include/c.h                          |   12 ++++++++++++
15 files changed, 29 insertions(+), 19 deletions(-)