Add pg_top-4.0.0

pg_top is 'top' for PostgreSQL. It is derived from Unix Top. Similar to
top, pg_top allows you to monitor PostgreSQL processes. Also see
pg_systat to monitor various PostgreSQL statistics tables. pg_top also
allows you to:

- View currently running SQL statement of a process.
- View query plan of a currently running SQL statement.
- View locks held by a process.
- Monitor remote databases that have the pg_proctab extension loaded.

(joerg)