[interfacekit] BRegion

Hi all.
Since there was no BRegion in our repository, and since Marc asked me to tackle 
this class for months ;P, I have done some work, played a bit with the debugger 
(BRegion involves lots of friend methods, which we have to implement as closely 
as R5 as possible), and I think that the public methods are implemented 
correctly.
What it's still missing are the following friend functions:

void and_region_complex(BRegion*, BRegion*, BRegion*);
void r_or(long, long, BRegion*, BRegion*, BRegion*, long*, long *);
void or_region_complex(BRegion*, BRegion*, BRegion*);
void sub_region_complex(BRegion*, BRegion*, BRegion*);
void r_sub(long , long, BRegion*, BRegion*, BRegion*, long*, long*);

I think I know what these function does, they are just hard to implement (I'm 
not a mathematician :))

Then there's 

void sort_trans(long *lptr1, long *lptr2, long count);

Which I still have to understand what it does,

and I'm reviewing cleanup_region_horizontal and cleanup_region_1, since they 
seem ok, but a bit ugly.

If there's someone who want to come here and help.... :P

Should I commit the partial work that I have done ?
There are also some inline functions which work with clipping_rects, that 
should be put in a private but "accessible" header (private/interface ?), since 
I guess they can be interesting even for our app server.

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