Change pglsn.sh so that it shows current WAL location.
Make pgtbl.sh use smarter SQL for creating simple table.
Refactor help message in pgdroppgbench.sh.
Allow pgtbl.sh to connect to server running on port other than 5432.

This commit changes pgtbl.sh so that it accepts the path of database
cluster. pgtbl.sh calculates the port number from the database
cluster and connects to the server using that database cluster.