Clean up -fixit output slightly

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@68278 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/FixItRewriter.cpp b/lib/Frontend/FixItRewriter.cpp
index a53d1e5..33ab0b7 100644
--- a/lib/Frontend/FixItRewriter.cpp
+++ b/lib/Frontend/FixItRewriter.cpp
@@ -57,8 +57,9 @@
     OutFile = &llvm::outs();
   } else {
     llvm::sys::Path Path(InFileName);
+    std::string Suffix = Path.getSuffix();
     Path.eraseSuffix();
-    Path.appendSuffix("cpp");
+    Path.appendSuffix("fixit." + Suffix);
     std::string Err;
     OutFile = new llvm::raw_fd_ostream(Path.toString().c_str(), 
                                        // set binary mode (critical for Windoze)