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

llvm-svn: 209389
diff --git a/clang/lib/Frontend/TextDiagnosticPrinter.cpp b/clang/lib/Frontend/TextDiagnosticPrinter.cpp
index e051614..7a2677b 100644
--- a/clang/lib/Frontend/TextDiagnosticPrinter.cpp
+++ b/clang/lib/Frontend/TextDiagnosticPrinter.cpp
@@ -43,7 +43,7 @@
 }
 
 void TextDiagnosticPrinter::EndSourceFile() {
-  TextDiag.reset(0);
+  TextDiag.reset(nullptr);
 }
 
 /// \brief Print any diagnostic option information to a raw_ostream.