Allow calling LLNotificationsUtil::add from any thread.

This makes LLStringUtil thread-safe by removing a rather unnecessary
LLFastTimer from LLStringUtil::format.

Same thing for LLTrans::getString and LLTrans::findString, where
even a comment stated that the author wasn't interested in measuring
cpu time at all. In this case I added some code back to make sure
that we're not calling LLTrans::getString() in an inner loop, which
was the reason that the LLFastTimer was added.

Made one string static to avoid 45000 look ups during login, which
kinda triggered the above test.

Finally, LLNotificationsUtil::add is made thread-safe by making
LLNotificationChannelBase::mItems thread-safe and defering a call
to LLNotifications::updateItem to the main thread when called
from another thread (using a little statemachine).

indra/llui/llnotifications.h

@@ -107,6 +107,7 @@
 #include "llxmlnode.h"
 #include "llnotificationptr.h"
 #include "llnotificationcontext.h"
+#include "aithreadsafe.h"
 
 namespace AIAlert { class Error; }
 
@@ -196,6 +197,7 @@ class LLNotification  :
 {
 LOG_CLASS(LLNotification);
 friend class LLNotifications;
+friend class UpdateItem;
 
 public:
 	// parameter object used to instantiate a new notification
@@ -566,9 +568,10 @@ class LLNotificationChannelBase :
 	public boost::signals2::trackable
 {
 	LOG_CLASS(LLNotificationChannelBase);
+	friend class UpdateItem;
 public:
 	LLNotificationChannelBase(LLNotificationFilter filter, LLNotificationComparator comp) : 
-		mFilter(filter), mItems(comp) 
+		mFilter(filter), mItems_sf(comp) 
 	{}
 	virtual ~LLNotificationChannelBase() {}
 	// you can also connect to a Channel, so you can be notified of
@@ -582,7 +585,9 @@ public:
 	const LLNotificationFilter& getFilter() { return mFilter; }
 
 protected:
-	LLNotificationSet mItems;
+	AIThreadSafeSimpleDC<LLNotificationSet> mItems_sf;
+	typedef AIAccess<LLNotificationSet> mItems_wat;
+	typedef AIAccessConst<LLNotificationSet> mItems_crat;
 	LLStandardSignal mChanged;
 	LLStandardSignal mPassedFilter;
 	LLStandardSignal mFailedFilter;