DRTVWR-418: Another fix for std::string::find() return type.

indra/newview/llviewermessage.cpp

@@ -2596,7 +2596,7 @@ void process_improved_im(LLMessageSystem *msg, void **user_data)
 
 			// The group notice packet does not have an AgentID.  Obtain one from the name cache.
 			// If last name is "Resident" strip it out so the cache name lookup works.
-			U32 index = original_name.find(" Resident");
+			std::string::size_type index = original_name.find(" Resident");
 			if (index != std::string::npos)
 			{
 				original_name = original_name.substr(0, index);