pgsql: Remove the xlog-centric "database system is ready" message and

Log Message:
-----------
Remove the xlog-centric "database system is ready" message and replace it with
"database system is ready to accept connections", which is issued by the
postmaster when it really is ready to accept connections.  Per proposal from
Markus Schiltknecht and subsequent discussion.

Modified Files:
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    pgsql/src/backend/access/transam:
        xlog.c (r1.261 -> r1.262)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/transam/xlog.c.diff?r1=1.261&r2=1.262)
    pgsql/src/backend/postmaster:
        postmaster.c (r1.516 -> r1.517)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/postmaster.c.diff?r1=1.516&r2=1.517)