pgsql: Make logging of extended-protocol commands a bit more consistent,

Log Message:
-----------
Make logging of extended-protocol commands a bit more consistent, per
discussion with Guillaume Smet.

Modified Files:
--------------
pgsql/src/backend/tcop:
postgres.c (r1.508 -> r1.509)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/tcop/postgres.c.diff?r1=1.508&r2=1.509)