Rework how master plans declare themselves. Also make "PlanIsBasePlan" not rely only on this being the bottom plan in the stack, but allow the plan to declare itself as such.

llvm-svn: 154351

lldb/source/Target/ThreadPlan.cpp

@@ -36,7 +36,8 @@ ThreadPlan::ThreadPlan(ThreadPlanKind kind, const char *name, Thread &thread, Vo
     m_plan_complete_mutex (Mutex::eMutexTypeRecursive),
     m_plan_complete (false),
     m_plan_private (false),
-    m_okay_to_discard (false)
+    m_okay_to_discard (false),
+    m_is_master_plan (false)
 {
     SetID (GetNextID());
 }