Get VS 2015 to use const int definitions

third_party/protobuf/src/google/protobuf/compiler/cpp/cpp_enum.cc

Index: third_party/protobuf/src/google/protobuf/compiler/cpp/cpp_enum.cc
diff --git a/third_party/protobuf/src/google/protobuf/compiler/cpp/cpp_enum.cc b/third_party/protobuf/src/google/protobuf/compiler/cpp/cpp_enum.cc
index 67c12d7abf9fd657995a6bbcdbd1cd46df690ebb..fda011a92ed40740812b532920ec8f8c40f8fe0c 100644
--- a/third_party/protobuf/src/google/protobuf/compiler/cpp/cpp_enum.cc
+++ b/third_party/protobuf/src/google/protobuf/compiler/cpp/cpp_enum.cc
@@ -232,9 +232,9 @@ void EnumGenerator::GenerateMethods(io::Printer* printer) {
   if (descriptor_->containing_type() != NULL) {
     // We need to "define" the static constants which were declared in the
     // header, to give the linker a place to put them.  Or at least the C++
-    // standard says we have to.  MSVC actually insists tha we do _not_ define
-    // them again in the .cc file.
-    printer->Print("#ifndef _MSC_VER\n");
+    // standard says we have to.  MSVC actually insists that we do _not_ define
+    // them again in the .cc file, prior to VC++ 2015.
+    printer->Print("#if !defined(_MSC_VER) || _MSC_VER >= 1900\n");
 
     vars["parent"] = ClassName(descriptor_->containing_type(), false);
     vars["nested_name"] = descriptor_->name();