pgsql: Andrew pointed out that the current fix didn't handle dates that

Log Message:
-----------
Andrew pointed out that the current fix didn't handle dates that were
near daylight savings time boudaries. This handles it properly, e.g.

test=> select '2005-04-03 04:00:00'::timestamp at time zone
'America/Los_Angeles';
timezone
------------------------
2005-04-03 07:00:00-04
(1 row)

Modified Files:
--------------
pgsql/src/backend/utils/adt:
date.c (r1.118 -> r1.119)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/date.c.diff?r1=1.118&r2=1.119)
datetime.c (r1.156 -> r1.157)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/datetime.c.diff?r1=1.156&r2=1.157)
formatting.c (r1.92 -> r1.93)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/formatting.c.diff?r1=1.92&r2=1.93)
nabstime.c (r1.141 -> r1.142)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/nabstime.c.diff?r1=1.141&r2=1.142)
timestamp.c (r1.143 -> r1.144)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/timestamp.c.diff?r1=1.143&r2=1.144)
pgsql/src/include/utils:
datetime.h (r1.55 -> r1.56)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/datetime.h.diff?r1=1.55&r2=1.56)