Add an erase() method to llvm::ThreadLocal.

llvm-svn: 109686
diff --git a/llvm/lib/System/Win32/ThreadLocal.inc b/llvm/lib/System/Win32/ThreadLocal.inc
index c8f7840..b8b933c 100644
--- a/llvm/lib/System/Win32/ThreadLocal.inc
+++ b/llvm/lib/System/Win32/ThreadLocal.inc
@@ -46,4 +46,8 @@
   assert(errorcode != 0);
 }
 
+void ThreadLocalImpl::removeInstance() {
+  setInstance(0);
+}
+
 }