[vala] libpq: fix freeing of Postgres.Notify

[Evan Nemerson <evann src gnome org>]

commit 57ffa01656e712679adfaf584ff4523f0b9d6a70
Author: Dmitry Vagin <dmitry2004 yandex ru>
Date:   Tue Jun 26 14:45:20 2012 -0700

    libpq: fix freeing of Postgres.Notify
    
    Fixes bug 678910.

 vapi/libpq.vapi |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/vapi/libpq.vapi b/vapi/libpq.vapi
index e47ca07..0e4be3e 100644
--- a/vapi/libpq.vapi
+++ b/vapi/libpq.vapi
@@ -89,11 +89,14 @@ namespace Postgres {
 		SOURCE_FUNCTION
 	}
 
-	[CCode (cname = "PGnotify")]
-	public struct Notify {
+	[Compact]
+	[CCode (cname = "PGnotify", free_function = "PQfreemem")]
+	public class Notify {
 		public string relname;
 		public int    be_pid;
 		public string extra;
+
+		private Notify ();
 	}
 
 	[CCode (cname = "PQnoticeReceiver")]