Temporary preprocessor hack to get around the Microsoft __identifier(x) extension.

Temporary preprocessor hack to get around the Microsoft __identifier(x) extension.
http://msdn.microsoft.com/en-us/library/hzc8ytsz(v=VS.100).aspx

Microsoft doc claims this is a C++/CLI feature but it is really always enabled.
This removes 2 error when parsing MFC code with clang.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@131051 91177308-0d34-0410-b5e6-96231b3b80d8