[PGAGENT] [PATCH] Remove wxWidget dependency

Please find the attached patch to remove the wxWidgets dependency, and added "Boost" dependency from the pgAgent code.

The original author of the patch is Neel Patel.

I have modified couple of things like:

- Using Locker class to work locking & unlocking of shared mutex always in tandem

- Using single pointer handler class for handling the memory leak of DBresult class

Please review it, and let us know the concerns.