Patch for - Allow server logs to be remotely read

The patch is attached for the following TODO item:

*Allow server logs to be remotely read.

Steps:

1. When the server starts (**pg_ctl start)**, the path of the postmaster file is stored
2. The user can access the logfile using the following 2 functions:
* pg_file_readlog(int linenumber) - Retrieves the string for the given line number
* **pg_file_countlog() - Retrieves the number of lines existing in the logfile*

I have implemented this based on the suggestions given in the hackers mailing list.
If you know a better way, please share it with me. Waiting for your reply.

Thanks
Dhanaraj