pgsql: Enhance pgbench -l option to add timestamp.

Log Message:
-----------
Enhance pgbench -l option to add timestamp. Patch contributed by Greg
Smith. Along with Japanese doc updation by Tasuo Ishii.

> This patch changes the way pgbench outputs its latency log files so that
> every transaction gets a timestamp and notes which transaction type was
> executed. It's a one-line change that just dumps some additional
> information that was already sitting in that area of code. I also made a
> couple of documentation corrections and clarifications on some of the more
> confusing features of pgbench.
>
> It's straightforward to parse log files in this format to analyze what
> happened during the test at a higher level than was possible with the
> original format. You can find some rough sample code to convert this
> latency format into CVS files and then into graphs at
> http://www.westnet.com/~gsmith/content/postgresql/pgbench.htm which I'll
> be expanding on once I get all my little patches sent in here.

Modified Files:
--------------
pgsql/contrib/pgbench:
README.pgbench (r1.16 -> r1.17)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pgbench/README.pgbench.diff?r1=1.16&r2=1.17)
README.pgbench_jis (r1.17 -> r1.18)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pgbench/README.pgbench_jis.diff?r1=1.17&r2=1.18)
pgbench.c (r1.63 -> r1.64)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pgbench/pgbench.c.diff?r1=1.63&r2=1.64)