LLViewerRegion WIP: Added all headers that are dragged in.

Most in particular llevents.h, which comes along with
the demand that the old events in llevent.h are put
in a namespace LLOldEvents. Made all changes necessary
to compile the rest of the code again (without changing
the actual code: it's still using the old events).

This patch also removes LLStopWhenHandled and LLStandardSignal
from indra/llui/llnotifications.h because those are
moved to llevents.h. That seems to be the only change
to indra/llui/llnotifications.h that isn't floater related,
so I left the rest of that file alone.

indra/newview/llnetmap.cpp

@@ -80,6 +80,8 @@
 #include "rlvhandler.h"
 // [/RLVa:KB]
 
+using namespace LLOldEvents;
+
 const F32 MAP_SCALE_MIN = 32;
 const F32 MAP_SCALE_MID = 256;
 const F32 MAP_SCALE_MAX = 4096;