[cairo] [API] Export region data type

[Soeren Sandmann]

M Joonas Pihlaja <jpihlaja at cc.helsinki.fi> writes:

> Just to chime in on the colour of the bike shed at this late date...

I just pushed the code, with signed integers for width/height. There
are reasonable arguments both for and against unsigned, so I am not
going to object if you or someone else change them back to unsigned.

News since last time:
        
        cairo_region_subtract_rectangle()
        API documentation
        minor bug fixes


Thanks,
Soren