Untested code is indeed buggy code.

Mozilla bug #603352.

Mozilla bug #603346

hb_ot_plan_t may be a better name, donno.

We now build our entire attack plan before jumping in.

Not hooked up just yet.

Correspond to the make_mutable() ones.

One in particular is not a straight getter: hb_font_unset_funcs() is
special because of the specific needs of the lifecycle management of
the user_data object.

See email thread "Should MarkToBase attachment zero the mark advance?"
started by Jonathan Kew on 23 August 2010 for details.