Rename Diagnostic to DiagnosticsEngine as per issue 5397


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@140478 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/driver/driver.cpp b/tools/driver/driver.cpp
index 64aa632..b9268df 100644
--- a/tools/driver/driver.cpp
+++ b/tools/driver/driver.cpp
@@ -375,7 +375,7 @@
     = new TextDiagnosticPrinter(llvm::errs(), DiagnosticOptions());
   DiagClient->setPrefix(llvm::sys::path::stem(Path.str()));
   llvm::IntrusiveRefCntPtr<DiagnosticIDs> DiagID(new DiagnosticIDs());
-  Diagnostic Diags(DiagID, DiagClient);
+  DiagnosticsEngine Diags(DiagID, DiagClient);
 
 #ifdef CLANG_IS_PRODUCTION
   const bool IsProduction = true;