pgsql-server: Ensure that the remainder of the current pg_clog page is

Log Message:
-----------
Ensure that the remainder of the current pg_clog page is zeroed during
startup, just to be sure that there's no leftover junk there.

Modified Files:
--------------
pgsql-server/src/backend/access/transam:
clog.c (r1.25 -> r1.26)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/access/transam/clog.c.diff?r1=1.25&r2=1.26)