Improve pg_restore docs

Hi,

From a quick discussion on hackers
(http://archives.postgresql.org/pgsql-hackers/2009-06/msg01434.php) it
appears the documentation can improve for pg_restore.

I've prepared some quick diff output from
pgsql/doc/src/sgml/ref/pg_restore.sgml for some changes that I think
would help. Note that I'm not entirely sure about the default namespace
from default_path .. please verify this before accepting. Edit as necessary.

291c291,292
< specific table.
---
> specific table. The default is taken from the
> <envar>default_path</envar> variable.
379c380,382
< Restore definition and/or data of named table only.
---
> Restore definition and/or data of named table only. This can be
> combined with the <option>-n</option> option to restore a table
> from a specific schema.

Thanks,

-Mike