cel_pgsql, cdr_pgsql, res_config_pgsql: Add PostgreSQL application_name support

This patch adds support for the PostgreSQL application_name connection setting.
When the appropriate PostgreSQL module's configuration is set with an
application name, the name will be passed to PostgreSQL on connection and
displayed in the database's pg_stat_activity view, as well as in CSV logs. This
aids in managing which applications/servers are connected to a PostgreSQL
database, as well as tracing the activity of those connections.

Review: https://reviewboard.asterisk.org/r/3591

ASTERISK-23737 #close
Reported by: Gergely Domodi
patches:
  pgsql_application_name.patch uploaded by Gergely Domodi (License 6610)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@418755 65c4cc65-6c06-0410-ace0-fbb531ad65f3