Kill a few more random stderr uses.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@90441 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/FixItRewriter.cpp b/lib/Frontend/FixItRewriter.cpp
index dddcaa9..4fa2b3c 100644
--- a/lib/Frontend/FixItRewriter.cpp
+++ b/lib/Frontend/FixItRewriter.cpp
@@ -66,7 +66,7 @@
         Rewrite.getRewriteBufferFor(MainFileID)) {
     *OutFile << std::string(RewriteBuf->begin(), RewriteBuf->end());
   } else {
-    std::fprintf(stderr, "Main file is unchanged\n");
+    Diag(FullSourceLoc(), diag::note_fixit_main_file_unchanged);
   }
   OutFile->flush();