[Cairo] renaming cairo_concat_matrix

[Carol Spears]

Carl Worth wrote:

>	cairo_set_matrix (cairo_t *cr, cairo_matrix_t *matrix);
>
>	cairo_default_matrix (cairo_t *cr);
>
>	/* XXX: There's been a proposal to add cairo_default_matrix_exact */
>
>	cairo_identity_matrix (cairo_t *cr);
>
>Any proposal should consider these as well.
>
>  
>
cairo_matrix_set
cairo_matrix_default
cairo_matrix_identity
cairo_matrix_other

carol