Embedd bitmaps into dataflow problem structures

[Paolo Bonzini]

> Can I ask you about the flattening of block_info array?
> Since we keep basic_block indexes dense, I guess I would not be scared of
> extra memory overhead for unused indexes.
> I wonder what the API sould be.  Currently there is
>    /* Array indexed by bb->index, that contains basic block problem and
>       solution specific information.  */
>    void **block_info;
> that is allocated at df_grow_bb_info and we have accestor functions.

Is it enough to add to the dfproblem structure the size of the bb-info 
structure?

Paolo