Clean up core module for building with Clang

This means removing unused private variables in random-variable-stream.{cc,h} and system-thread.h and fixing removing bad static_casts in calendar-scheduler.cc.

src/core/model/calendar-scheduler.cc

@@ -131,7 +131,11 @@ CalendarScheduler::PeekNext (void) const
   NS_ASSERT (!IsEmpty ());
   uint32_t i = m_lastBucket;
   uint64_t bucketTop = m_bucketTop;
-  Scheduler::Event minEvent = { static_cast<uint64_t>(0), { static_cast<uint32_t>(~0), static_cast<uint32_t>(~0)}};
+  Scheduler::Event minEvent;
+  minEvent.impl = 0;
+  minEvent.key.m_ts = ~0;
+  minEvent.key.m_uid = ~0;
+  minEvent.key.m_context = 0;
   do
     {
       if (!m_buckets[i].empty ())

src/core/model/random-variable-stream.cc

@@ -1170,8 +1170,6 @@ TriangularRandomVariable::GetTypeId (void)
   return tid;
 }
 TriangularRandomVariable::TriangularRandomVariable ()
-  :
-  m_mode (0.5)
 {
   // m_mean, m_min, and m_max are initialized after constructor by
   // attributes

src/core/model/random-variable-stream.h

@@ -1982,10 +1982,6 @@ private:
 
   /// The upper bound on values that can be returned by this RNG stream.
   double m_max;
-
-  /// It's easier to work with the mode internally instead of the
-  /// mean.  They are related by the simple: mean = (min+max+mode)/3.
-  double m_mode;
 };
 
 /**

src/core/model/system-thread.h

@@ -148,7 +148,6 @@ private:
 
   Callback<void> m_callback;
   pthread_t m_thread;
-  void *    m_ret;
 #endif 
 };