[cairo] API Shakeup: Abbreviation hunt: cairo_init_clip and cairo_concat_matrix

[mental at rydia.net]

Quoting Carl Worth <cworth at cworth.org>:

> Interestingly enough, cairo_append_transform doesn't strike me as
> having the same problem, since no matter the math, it is clear
> that the operation here is to provide an additional
transformation.
> I have been tempted to rename cairo_matrix_t to cairo_transform_t,
> (to focus on the behavior, not its mathematical implementation).
> Owen convinced me once before that it wasn't worth changing, but
> now that we're already changing almost everything else...

I'd be in favor of that myself.  Though cairo_transform_t is a bit
verbose to type...

Would you be mad at me if I suggested cairo_xform_t? :)

-mental