Preprocessing inside {#offsetof #} {#sizeof #} etc

`linux/input.h` uses defines to provide different public aliases for struct fields:

```c
struct input_event {
#if (__BITS_PER_LONG != 32 || !defined(__USE_TIME_BITS64)) && !defined(__KERNEL__)
struct timeval time;
#define input_event_sec time.tv_sec
#define input_event_usec time.tv_usec
#else
__kernel_ulong_t __sec;
#if defined(__sparc__) && defined(__arch64__)
unsigned int __usec;
#else
__kernel_ulong_t __usec;
#endif
#define input_event_sec __sec
#define input_event_usec __usec
#endif
__u16 type;
__u16 code;
__s32 value;
};
```

Unfortunately it doesn't seem like c2hs wants to handle code like `{#offsetof input_event->input_event_usec #}`