[PATCH] more enhancements to df on the mainline.

[Daniel Berlin]

> I have enclosed a new version of the patch, the first version had the frags 
> for the other two dependent patches in it.
>
> Sorry,
>
> Kenny

Oh, I should point out why the hook takes a void * instead of a bitmap.
Not everything that wants to include the target hooks includes something 
that declares or forward declares bitmap, however, forward declaring it 
simply caused errors.

In the end, rather than add bitmap.h to the include list of everything on 
the planet, i void *'d the hook and just cast it where we actually are 
touching it.

I guess we could just use struct bitmap_head_def * everywhere, but that 
seems uglier to me (because that would require changing if the typedef 
ever changes, while the void * would not).

--Dan