kernel32: Remove unneeded casts

[Robert Shearman]

Andrew Talbot wrote:
>    /* All local heap allocations are aligned on 4-byte boundaries */
>  #define LALIGN(word)          (((word) + 3) & ~3)
>  
> -#define ARENA_PTR(ptr,arena)       ((LOCALARENA *)((char*)(ptr)+(arena)))
> +#define ARENA_PTR(ptr,arena)       ((LOCALARENA *)((ptr)+(arena)))

Don't remove casts from macros like this as they then won't be safe if 
the type that is passed in is changed to something else (like void *).

-- 
Rob Shearman