Added AIFetchInventoryFolder and more.

Added a new statemachine AIFetchInventoryFolder, which can be used
to fetch the contents of a folder by name or UUID.

Also added AIEvent (and one event,
AIEvent::LLInventoryModel_mIsAgentInvUsable_true, which is needed
for AIFetchInventoryFolder).

Fixed LLInventoryModel::sBackgroundFetchActive to correctly reflect
whether or not LLInventoryModel::backgroundFetch is added to
gIdleCallbacks.

Avoid duplicated entries in sFetchQueue.

Reset sFullFetchStarted in LLInventoryModel::stopBackgroundFetch to
allow for a renewed full fetch when some single-folder fetch stops it.

Added AIStateMachine::mQueued to make calling 'cont()' more robust:
calling cont() / idle() / cont() on a row would otherwise add a
statemachine twice to the active list, which would cause a crash
when it's killed.

indra/newview/llhudeffectlookat.h

@@ -34,6 +34,7 @@
 #define LL_LLHUDEFFECTLOOKAT_H
 
 #include "llhudeffect.h"
+#include "llframetimer.h"
 
 class LLViewerObject;
 class LLVOAvatar;