Send group notices through the same messaging module mechanism used to send group chat to avoid timeout issues when sending messages to large groups.

Only implementing for XmlRpcGroups initially to test.
May require MessageOnlineUsersOnly = true in [Groups] to be effective.
In relation to http://opensimulator.org/mantis/view.php?id=7037

OpenSim/Region/Framework/Interfaces/IGroupsMessagingModule.cs

@@ -25,6 +25,7 @@
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+using System;
 using OpenMetaverse;
 using OpenSim.Framework;
 
@@ -57,7 +58,7 @@ namespace OpenSim.Region.Framework.Interfaces
         bool StartGroupChatSession(UUID agentID, UUID groupID);
         
         /// <summary>
-        /// Send a message to an entire group.
+        /// Send a message to each member of a group whose chat session is active.
         /// </summary>
         /// <param name="im">
         /// The message itself.  The fields that must be populated are
@@ -69,5 +70,23 @@ namespace OpenSim.Region.Framework.Interfaces
         /// </param>
         /// <param name="groupID"></param>
         void SendMessageToGroup(GridInstantMessage im, UUID groupID);
+
+        /// <summary>
+        /// Send a message to all the members of a group that fulfill a condition.
+        /// </summary>
+        /// <param name="im">
+        /// The message itself.  The fields that must be populated are
+        /// 
+        /// imSessionID - Populate this with the group ID (session ID and group ID are currently identical)
+        /// fromAgentName - Populate this with whatever arbitrary name you want to show up in the chat dialog
+        /// message - The message itself
+        /// dialog - This must be (byte)InstantMessageDialog.SessionSend
+        /// </param>
+        /// <param name="groupID"></param>
+        /// <param name="sendCondition">
+        /// The condition that must be met by a member for the message to be sent.  If null then the message is sent
+        /// if the chat session is active.
+        /// </param>
+        void SendMessageToGroup(GridInstantMessage im, UUID groupID, Func<GroupMembersData, bool> sendCondition);
     }
 }