Fix PR1966 by ignoring non-error diagnostics from system headers even if they are 
*mapped* onto errors.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@46686 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/Driver/TextDiagnostics.h b/Driver/TextDiagnostics.h
index 82ea116..9b8d9fb 100644
--- a/Driver/TextDiagnostics.h
+++ b/Driver/TextDiagnostics.h
@@ -34,8 +34,7 @@
 
   void setHeaderSearch(HeaderSearch &HS) { TheHeaderSearch = &HS; }
 
-  virtual bool IgnoreDiagnostic(Diagnostic::Level Level, 
-                                FullSourceLoc Pos);
+  virtual bool isInSystemHeader(FullSourceLoc Pos) const;
 
   virtual void HandleDiagnostic(Diagnostic &Diags, Diagnostic::Level DiagLevel,
                                 FullSourceLoc Pos,