Added checkboxes to groups list for visibility, groupchat, and notices...

-Required addition of an extra texture overlay for list headers, as normal button overlay is used for sort arrows.
-Added padding to italic text in scroll list, as the text clipped outside of the element.
-Groups list is now sortable and has header visible.
-'none' entry always be first in the list, regardless of sort order.
-LLGroupMgrGroupData::mListInProfile removed. Was unreferenced and always false. LLGroupMgrGroupData doesn't handle show/chat/notify properties

indra/newview/llagent.cpp

@@ -2488,8 +2488,6 @@ BOOL LLAgent::setGroupContribution(const LLUUID& group_id, S32 contribution)
 	return FALSE;
 }
 
-void update_group_floaters(const LLUUID& group_id);
-
 BOOL LLAgent::setUserGroupFlags(const LLUUID& group_id, BOOL accept_notices, BOOL list_in_profile)
 {
 	S32 count = mGroups.count();