[C++11] Fix break due to MSVC bug.

MSVC (2012, 2013, 2013 Nov CTP) fail on the following code:

int main() {
  int arr[] = {1, 2};
  for (int i : arr)
    do {} while (0);
}

The fix is to put {} around the for loop. I've reported this to the MSVC
team.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203371 91177308-0d34-0410-b5e6-96231b3b80d8