pgsql: Fix assorted breakage in to_char()'s OF format option.

Fix assorted breakage in to_char()'s OF format option.

In HEAD, fix incorrect field width for hours part of OF when tm_gmtoff is
negative.  This was introduced by commit 2d87eedc1d4468d3 as a result of
falsely applying a pattern that's correct when + signs are omitted, which
is not the case for OF.

In 9.4, fix missing abs() call that allowed a sign to be attached to the
minutes part of OF.  This was fixed in 9.5 by 9b43d73b3f9bef27, but for
inscrutable reasons not back-patched.

In all three versions, ensure that the sign of tm_gmtoff is correctly
reported even when the GMT offset is less than 1 hour.

Add regression tests, which evidently we desperately need here.

Thomas Munro and Tom Lane, per report from David Fetter

Branch
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REL9_5_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/d0a585c6997de6aebd5866c9c1791a1badfcee0a

Modified Files
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src/backend/utils/adt/formatting.c        | 10 ++++--
src/test/regress/expected/timestamptz.out | 51 +++++++++++++++++++++++++++++++
src/test/regress/sql/timestamptz.sql      | 17 +++++++++++
3 files changed, 75 insertions(+), 3 deletions(-)