pgsql: Remove unnecessary parentheses in datetime/timestamp code.

Log Message:
-----------
Remove unnecessary parentheses in datetime/timestamp code.

Modified Files:
--------------
pgsql/src/backend/utils/adt:
datetime.c (r1.140 -> r1.141)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/datetime.c.diff?r1=1.140&r2=1.141)
timestamp.c (r1.119 -> r1.120)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/timestamp.c.diff?r1=1.119&r2=1.120)