Add application_name to PostgreSQL driver

PostgreSQL allows the user to set the application_name is connecting
to database. It is useful for monitoring purposes.
Currently one could just manually add 'application_name=foo' to DSN,
but having a parameter eases setting it using DoctrineBundle.

docs/en/reference/configuration.rst

@@ -259,6 +259,8 @@ pdo\_pgsql
    the server's certificate will be verified to be signed by one of these
    authorities.
    See http://www.postgresql.org/docs/9.0/static/libpq-connect.html#LIBPQ-CONNECT-SSLROOTCERT
+-  ``application_name`` (string): Name of the application that is
+   connecting to database. Optional. It will be displayed at ``pg_stat_activity``.
 
 PostgreSQL behaves differently with regard to booleans when you use
 ``PDO::ATTR_EMULATE_PREPARES`` or not. To switch from using ``'true'``
@@ -290,7 +292,7 @@ pdo\_oci / oci8
    database.
 -  ``instancename`` (string): Optional parameter, complete whether to
    add the INSTANCE_NAME parameter in the connection. It is generally used
-   to connect to an Oracle RAC server to select the name of a particular instance.   
+   to connect to an Oracle RAC server to select the name of a particular instance.
 
 
 pdo\_sqlsrv / sqlsrv

lib/Doctrine/DBAL/Driver/PDOPgSql/Driver.php

@@ -91,7 +91,7 @@ private function _constructPdoDsn(array $params)
         } else {
             // Used for temporary connections to allow operations like dropping the database currently connected to.
             // Connecting without an explicit database does not work, therefore "postgres" database is used
-            // as it is certainly present in every server setup. 
+            // as it is certainly present in every server setup.
             $dsn .= 'dbname=postgres' . ' ';
         }
 
@@ -103,6 +103,10 @@ private function _constructPdoDsn(array $params)
             $dsn .= 'sslrootcert=' . $params['sslrootcert'] . ' ';
         }
 
+        if (isset($params['application_name'])) {
+            $dsn .= 'application_name=' . $params['application_name'] . ' ';
+        }
+
         return $dsn;
     }