Uninitialized read undetected on Win 64bit

Using drmemory 2.1.0 on the following code with Visual Studio 2013:

```cpp
#include
int main()
{
int x;
double y;
printf("%i %f\n", x, y);
}
```

Building for 32 bit [Release with debug info] gives (correctly):

`2 unique, 2 total uninitialized access(es)`

But building for 64 bit gives `NO ERRORS FOUND`.

I tried more complex code with uninitialized class members with the same results.