Fix error in the Win32 implementation pointed out by Howard Su.

llvm-svn: 74248

llvm/lib/System/Win32/ThreadLocal.inc

@@ -42,7 +42,7 @@ const void* ThreadLocalImpl::getInstance() {
 
 void ThreadLocalImpl::setInstance(const void* d){
   DWORD* tls = static_cast<DWORD*>(data);
-  int errorcode = TlsSetValue(*tls, d);
+  int errorcode = TlsSetValue(*tls, const_cast<void*>(d));
   assert(errorcode == 0);
 }