Add SOG.HasPrivateAttachmentPoint to tell if a SOG has a private attachment point. HUDs attachment points are private.

Change SOP.SendFullUpdateToClient() and SoundModule.PlayAttachedSound() to use this rather than different magic number formulations.
This also corrects a bug in PlayAttachedSound() where the code assumed that all attachment points over 30 were HUDs.
It appears this is no longer true with Neck and Root (Avatar Center)

OpenSim/Region/CoreModules/World/Sound/SoundModule.cs

@@ -78,11 +78,8 @@ namespace OpenSim.Region.CoreModules.World.Sound
 
                 if (grp.IsAttachment)
                 {
-                    if (grp.AttachmentPoint > 30) // HUD
-                    {
-                        if (sp.ControllingClient.AgentId != grp.OwnerID)
-                            return;
-                    }
+                    if (grp.HasPrivateAttachmentPoint && sp.ControllingClient.AgentId != grp.OwnerID)
+                        return;
 
                     if (sp.ControllingClient.AgentId == grp.OwnerID)
                         dis = 0;

OpenSim/Region/Framework/Scenes/SceneObjectGroup.cs

@@ -180,6 +180,22 @@ namespace OpenSim.Region.Framework.Scenes
             }
         }
 
+        /// <summary>
+        /// If this scene object has an attachment point then indicate whether there is a point where
+        /// attachments are perceivable by avatars other than the avatar to which this object is attached.
+        /// </summary>
+        /// <remarks>
+        /// HUDs are not perceivable by other avatars.
+        /// </remarks>
+        public bool HasPrivateAttachmentPoint
+        {
+            get
+            {
+                return AttachmentPoint >= (uint)OpenMetaverse.AttachmentPoint.HUDCenter2
+                    && AttachmentPoint <= (uint)OpenMetaverse.AttachmentPoint.HUDBottomRight;
+            }
+        }
+
         public void ClearPartAttachmentData()
         {
             AttachmentPoint = 0;

OpenSim/Region/Framework/Scenes/SceneObjectPart.cs

@@ -2573,8 +2573,9 @@ namespace OpenSim.Region.Framework.Scenes
             if (ParentGroup.IsDeleted)
                 return;
 
-            if (ParentGroup.IsAttachment && (ParentGroup.AttachedAvatar != remoteClient.AgentId) &&
-                (ParentGroup.AttachmentPoint >= 31) && (ParentGroup.AttachmentPoint <= 38))
+            if (ParentGroup.IsAttachment
+                && ParentGroup.AttachedAvatar != remoteClient.AgentId
+                && ParentGroup.HasPrivateAttachmentPoint)
                 return;
 
             if (remoteClient.AgentId == OwnerID)