sim: have a curTick per eventq

This patch adds a _curTick variable to an eventq. This variable is updated
whenever an event is serviced in function serviceOne(), or all events upto
a particular time are processed in function serviceEvents(). This change
helps when there are eventqs that do not make use of curTick for scheduling
events.

src/sim/core.hh

@@ -39,12 +39,10 @@
 #include <string>
 
 #include "base/types.hh"
+#include "sim/eventq.hh"
 
 /// The universal simulation clock.
-extern Tick _curTick;
-
-inline Tick curTick() { return _curTick; }
-inline void curTick(Tick newVal) { _curTick = newVal; }
+inline Tick curTick() { return mainEventQueue.getCurTick(); }
 
 const Tick retryTime = 1000;