#sizeof doesn't work on struct fields

Trying to c2hs the following Foo.chs fails with "The phrase '.' is not allowed here." I want to get back 10. Replacing #sizeof with #offsetof causes c2hs to succeed. I think `#sizeof` should evaluate similarly to `sizeof` in C++ (`sizeof(Foo::bar)`). (I don't know how it can be done straightforwardly in C.)

```
/* Foo.h */
struct Foo {
char bar[10];
};
```

```
-- Foo.chs

#include "Foo.h"

module Foo where

sizeOfFooBar :: Int
sizeOfFooBar = {#sizeof Foo.bar#}
```