[gnome-contacts] Fix build with latest vala

[Alexander Larsson <alexl src gnome org>]

commit 1dbdbc5aa9105f6493478132b95ee901c1a44045
Author: Alexander Larsson <alexl redhat com>
Date:   Tue Jan 17 16:11:24 2012 +0100

    Fix build with latest vala

 src/contacts-linking.vala |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/contacts-linking.vala b/src/contacts-linking.vala
index 2a2f0ce..dc1f380 100644
--- a/src/contacts-linking.vala
+++ b/src/contacts-linking.vala
@@ -21,7 +21,7 @@ using Folks;
 using Gee;
 
 namespace Contacts {
-  internal abstract class PersonaAttribute : Object {
+  public abstract class PersonaAttribute : Object {
     public string property_name;
 
     public static HashSet<PersonaAttribute> create_set () {