This was a bizzare piece of API that I inherited from cairo. It has
been wrong adding them to cairo in the first place. Remove them before
someone uses them!
Unicode data providers can now be subclassed, including support for
chain-up. The interface should now be nicely bindable, as well.
Also fix glib unicode funcs that where broken after hb_script_t
changes. Nicely caught by the test-unicode.c added in this commit.
This includes HB_DIRECTION_INVALID and HB_SCRIPT_INVALID.
The INVALID will cause a "guess whatever from the text" in hb_shape().
While it's not ideal, it works better than the previous defaults at
least (HB_DIRECTION_LTR and HB_SCRIPT_COMMON).
The problem with HB_TAG_STR() was that it expected a string of size 4
exactly, and unlike hb_tag_from_string() it doesn't pad the tag with
space characters. So, the new name is more appropriate.