pgsql: Suppress possibly-uninitialized-variable warnings from gcc 4.5.

Suppress possibly-uninitialized-variable warnings from gcc 4.5.

It appears that gcc 4.5 can issue such warnings for whole structs, not
just scalar variables as in the past.  Refactor some pg_dump code slightly
so that the OutputContext local variables are always initialized, even
if they won't be used.  It's cheap enough to not be worth worrying about.

Branch
------
master

Details
-------
http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=e2627258c3cc43b8b00c5c29c35933a33259e718

Modified Files
--------------
src/bin/pg_dump/pg_backup_archiver.c |   44 ++++++++++++++++++++++-----------
src/bin/pg_dump/pg_backup_archiver.h |    6 ----
2 files changed, 29 insertions(+), 21 deletions(-)