[C++11] Use 'nullptr'. Frontend edition.

llvm-svn: 209389
diff --git a/clang/lib/Frontend/PrintPreprocessedOutput.cpp b/clang/lib/Frontend/PrintPreprocessedOutput.cpp
index 94b3275..8c32c24 100644
--- a/clang/lib/Frontend/PrintPreprocessedOutput.cpp
+++ b/clang/lib/Frontend/PrintPreprocessedOutput.cpp
@@ -162,7 +162,8 @@
                    const Token &Tok) {
     return ConcatInfo.AvoidConcat(PrevPrevTok, PrevTok, Tok);
   }
-  void WriteLineInfo(unsigned LineNo, const char *Extra=0, unsigned ExtraLen=0);
+  void WriteLineInfo(unsigned LineNo, const char *Extra=nullptr,
+                     unsigned ExtraLen=0);
   bool LineMarkersAreDisabled() const { return DisableLineMarkers; }
   void HandleNewlinesInToken(const char *TokStr, unsigned Len);
 
@@ -220,7 +221,7 @@
     }
   } else if (!DisableLineMarkers) {
     // Emit a #line or line marker.
-    WriteLineInfo(LineNo, 0, 0);
+    WriteLineInfo(LineNo, nullptr, 0);
   } else {
     // Okay, we're in -P mode, which turns off line markers.  However, we still
     // need to emit a newline between tokens on different lines.