pgsql: BDST should be "British double SUMMER time", not Standard time.

Log Message:
-----------
BDST should be "British double SUMMER time", not Standard time.
Per John Smith.

Modified Files:
--------------
pgsql/doc/src/sgml:
datetime.sgml (r2.43 -> r2.44)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/datetime.sgml.diff?r1=2.43&r2=2.44)