libpq: Fix memory leak

If a client encoding is specified as a connection parameter (or
environment variable), internal storage allocated for it would never
be freed.

src/interfaces/libpq/fe-connect.c

@@ -2749,6 +2749,8 @@ freePGconn(PGconn *conn)
 		free(conn->events[i].name);
 	}
 
+	if (conn->client_encoding_initial)
+		free(conn->client_encoding_initial);
 	if (conn->events)
 		free(conn->events);
 	if (conn->pghost)