[C++] Use 'nullptr'.

llvm-svn: 207394
diff --git a/llvm/lib/DebugInfo/DWARFDebugLine.h b/llvm/lib/DebugInfo/DWARFDebugLine.h
index a336f49..890eb28 100644
--- a/llvm/lib/DebugInfo/DWARFDebugLine.h
+++ b/llvm/lib/DebugInfo/DWARFDebugLine.h
@@ -24,7 +24,7 @@
 public:
   DWARFDebugLine(const RelocAddrMap* LineInfoRelocMap) : RelocMap(LineInfoRelocMap) {}
   struct FileNameEntry {
-    FileNameEntry() : Name(0), DirIdx(0), ModTime(0), Length(0) {}
+    FileNameEntry() : Name(nullptr), DirIdx(0), ModTime(0), Length(0) {}
 
     const char *Name;
     uint64_t DirIdx;