[C++11] Make use of 'nullptr' in the Support library.

llvm-svn: 205697
diff --git a/llvm/lib/Support/IntervalMap.cpp b/llvm/lib/Support/IntervalMap.cpp
index 4dfcc40..e11a7f2 100644
--- a/llvm/lib/Support/IntervalMap.cpp
+++ b/llvm/lib/Support/IntervalMap.cpp
@@ -58,7 +58,7 @@
     }
   } else if (height() < Level)
     // end() may have created a height=0 path.
-    path.resize(Level + 1, Entry(0, 0, 0));
+    path.resize(Level + 1, Entry(nullptr, 0, 0));
 
   // NR is the subtree containing our left sibling.
   --path[l].offset;