pgsql: Fix up hash functions for datetime datatypes so that they don't

Log Message:
-----------
Fix up hash functions for datetime datatypes so that they don't take
unwarranted liberties with int8 vs float8 values for these types.
Specifically, be sure to apply either hashint8 or hashfloat8 depending
on HAVE_INT64_TIMESTAMP.  Per my gripe of even date.

Modified Files:
--------------
    pgsql/src/backend/utils/adt:
        date.c (r1.133 -> r1.134)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/date.c.diff?r1=1.133&r2=1.134)
        timestamp.c (r1.178 -> r1.179)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/timestamp.c.diff?r1=1.178&r2=1.179)
    pgsql/src/include/catalog:
        catversion.h (r1.413 -> r1.414)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h.diff?r1=1.413&r2=1.414)
        pg_amproc.h (r1.65 -> r1.66)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_amproc.h.diff?r1=1.65&r2=1.66)
        pg_proc.h (r1.461 -> r1.462)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h.diff?r1=1.461&r2=1.462)
    pgsql/src/include/utils:
        date.h (r1.37 -> r1.38)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/date.h.diff?r1=1.37&r2=1.38)
        timestamp.h (r1.70 -> r1.71)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/timestamp.h.diff?r1=1.70&r2=1.71)
    pgsql/src/test/regress/expected:
        opr_sanity.out (r1.75 -> r1.76)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/opr_sanity.out.diff?r1=1.75&r2=1.76)
    pgsql/src/test/regress/sql:
        opr_sanity.sql (r1.61 -> r1.62)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/opr_sanity.sql.diff?r1=1.61&r2=1.62)