Allow \n for newlines in expected error messages.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@58198 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/Driver/DiagChecker.cpp b/Driver/DiagChecker.cpp
index 6f7ea0b..51f3979 100644
--- a/Driver/DiagChecker.cpp
+++ b/Driver/DiagChecker.cpp
@@ -78,6 +78,10 @@
     }
 
     std::string Msg(Comment.substr(OpenDiag, CloseDiag - OpenDiag));
+    size_type FindPos;
+    while((FindPos = Msg.find("\\n")) != std::string::npos) {
+      Msg.replace(FindPos, 2, "\n");
+    }
     ExpectedDiags.push_back(std::make_pair(Pos, Msg));
     ColNo = CloseDiag + 2;
   }