Minor inconsistencies

Hello!

I've prepared a patch to add some missing periods and tags.
I also suggest the following change in pgbench.sgml:
-   Here is some example output generated with these options:
+   Here is some example output generated with this option:
since I believe that this is the example for the --aggregate-interval 
option.
Please take a look.

-- 
Ekaterina Kiryanova
Technical Writer
Postgres Professional
the Russian PostgreSQL Company