pgsql: Attempt to fix breakage caused by signed integer conversion patc

Attempt to fix breakage caused by signed integer conversion patch.

Use INT_MIN rather than INT32_MIN as we do elsewhere in the code, and
try to work around nonexistence of INT64_MIN if necessary. Adjust the
new regression tests to something hopefully saner, per observation by
Tom Lane.

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=815810ed315a6d21203ec75a11f742f5ed655418

Modified Files
--------------
src/backend/utils/adt/numutils.c | 12 +++++++++++-
src/test/regress/expected/int2.out | 12 ++++++------
src/test/regress/expected/int4.out | 14 +++++++-------
src/test/regress/expected/int8.out | 18 +++++++++---------
src/test/regress/sql/int2.sql | 4 ++--
src/test/regress/sql/int4.sql | 6 +++---
src/test/regress/sql/int8.sql | 6 +++---
7 files changed, 41 insertions(+), 31 deletions(-)