TODO: Split out pg_resetxlog output into pre- and post-sections

This patch implements the following TODO item:

Split out pg_resetxlog output into pre- and post-sections

http://archives.postgresql.org/pgsql-hackers/2010-08/msg02040.php

On execution of pg_resetxlog using the option -n
1. It will display values in two section.
2. First section will be called as "Current pg_control values or Guess pg_control values".
3. In first section, it will display all current (i.e. before change) values of control file or guessed values.
4. Second section will be called as "Values to be used after reset".
5. In second section, it will display new values of parameters to be reset as per user request.

Please provide your opinion or expectation out of this patch.

I will add the same to November commitFest.

Thanks and Regards,
Kumar Rajeev Rastogi